4:18 p.m.
We actually use nrexceptional for very little these days. It's a minor
pain to keep in sync with nrpages, but the pain becomes much bigger
with the THP patches because we don't know how many indices a shadow
entry occupies. It's easier to just remove it than keep it accurate.
Also, we save 8 bytes per inode which is nothing to sneeze at; on my
laptop, it would improve shmem_inode_cache from 22 to 23 objects per
16kB, and inode_cache from 26 to 27 objects. Combined, that saves
a megabyte of memory from a combined usage of 25MB for both caches.
Unfortunately, ext4 doesn't cross a magic boundary, so it doesn't save
any memory for ext4.
Matthew Wilcox (Oracle) (4):
mm: Introduce and use mapping_empty
mm: Stop accounting shadow entries
dax: Account DAX entries as nrpages
mm: Remove nrexceptional from inode
fs/block_dev.c | 2 +-
fs/dax.c | 8 ++++----
fs/gfs2/glock.c | 3 +--
fs/inode.c | 2 +-
include/linux/fs.h | 2 --
include/linux/pagemap.h | 5 +++++
mm/filemap.c | 16 ----------------
mm/swap_state.c | 4 ----
mm/truncate.c | 19 +++----------------
mm/workingset.c | 1 -
10 files changed, 15 insertions(+), 47 deletions(-)
--
2.28.0
4:18 p.m.
New subject: [PATCH v2 1/4] mm: Introduce and use mapping_empty
Instead of checking the two counters (nrpages and nrexceptional), we
can just check whether i_pages is empty.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
---
fs/block_dev.c | 2 +-
fs/dax.c | 2 +-
fs/gfs2/glock.c | 3 +--
include/linux/pagemap.h | 5 +++++
mm/truncate.c | 18 +++---------------
5 files changed, 11 insertions(+), 19 deletions(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 9e84b1928b94..34105f66e12f 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -79,7 +79,7 @@ static void kill_bdev(struct block_device *bdev)
{
struct address_space *mapping = bdev->bd_inode->i_mapping;
- if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
+ if (mapping_empty(mapping))
return;
invalidate_bh_lrus();
diff --git a/fs/dax.c b/fs/dax.c
index 5b47834f2e1b..53ed0ab8c958 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -965,7 +965,7 @@ int dax_writeback_mapping_range(struct address_space *mapping,
if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
return -EIO;
- if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
+ if (mapping_empty(mapping) || wbc->sync_mode != WB_SYNC_ALL)
return 0;
trace_dax_writeback_range(inode, xas.xa_index, end_index);
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 5441c17562c5..bfad01ce096d 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -273,8 +273,7 @@ static void __gfs2_glock_put(struct gfs2_glock *gl)
if (mapping) {
truncate_inode_pages_final(mapping);
if (!gfs2_withdrawn(sdp))
- GLOCK_BUG_ON(gl, mapping->nrpages ||
- mapping->nrexceptional);
+ GLOCK_BUG_ON(gl, !mapping_empty(mapping));
}
trace_gfs2_glock_put(gl);
sdp->sd_lockstruct.ls_ops->lm_put_lock(gl);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index dc3390e6ee3e..86143d36d028 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -18,6 +18,11 @@
struct pagevec;
+static inline bool mapping_empty(struct address_space *mapping)
+{
+ return xa_empty(&mapping->i_pages);
+}
+
/*
* Bits in mapping->flags.
*/
diff --git a/mm/truncate.c b/mm/truncate.c
index 11ef90d7e3af..58524aaf67e2 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -342,7 +342,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
struct page * page;
bool partial_end;
- if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
+ if (mapping_empty(mapping))
goto out;
/*
@@ -470,9 +470,6 @@ EXPORT_SYMBOL(truncate_inode_pages);
*/
void truncate_inode_pages_final(struct address_space *mapping)
{
- unsigned long nrexceptional;
- unsigned long nrpages;
-
/*
* Page reclaim can not participate in regular inode lifetime
* management (can't call iput()) and thus can race with the
@@ -482,16 +479,7 @@ void truncate_inode_pages_final(struct address_space *mapping)
*/
mapping_set_exiting(mapping);
- /*
- * When reclaim installs eviction entries, it increases
- * nrexceptional first, then decreases nrpages. Make sure we see
- * this in the right order or we might miss an entry.
- */
- nrpages = mapping->nrpages;
- smp_rmb();
- nrexceptional = mapping->nrexceptional;
-
- if (nrpages || nrexceptional) {
+ if (!mapping_empty(mapping)) {
/*
* As truncation uses a lockless tree lookup, cycle
* the tree lock to make sure any ongoing tree
@@ -657,7 +645,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
int ret2 = 0;
int did_range_unmap = 0;
- if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
+ if (mapping_empty(mapping))
goto out;
pagevec_init(&pvec);
--
2.28.0
9:42 p.m.
New subject: [PATCH v2 1/4] mm: Introduce and use mapping_empty
On Mon, Oct 26, 2020 at 03:18:46PM +0000, Matthew Wilcox (Oracle) wrote:
Instead of checking the two counters (nrpages and nrexceptional), we
can just check whether i_pages is empty.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
Acked-by: Johannes Weiner <hannes(a)cmpxchg.org>
Heh, I was looking for the fs/inode.c hunk here, because I remember
those BUG_ONs in the inode free path. Found it in the last patch - I
guess they escaped grep but the compiler let you know? :-)
10:18 p.m.
New subject: [PATCH v2 1/4] mm: Introduce and use mapping_empty
On Thu, Jan 21, 2021 at 03:42:31PM -0500, Johannes Weiner wrote:
On Mon, Oct 26, 2020 at 03:18:46PM +0000, Matthew Wilcox (Oracle)
wrote:
> Instead of checking the two counters (nrpages and nrexceptional), we
> can just check whether i_pages is empty.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
> Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
Acked-by: Johannes Weiner <hannes(a)cmpxchg.org>
Heh, I was looking for the fs/inode.c hunk here, because I remember
those BUG_ONs in the inode free path. Found it in the last patch - I
guess they escaped grep but the compiler let you know? :-)
Heh, I forget now! I think I did it that way on purpose, but now I
forget what that purpose was!
4:18 p.m.
New subject: [PATCH v2 2/4] mm: Stop accounting shadow entries
We no longer need to keep track of how many shadow entries are
present in a mapping. This saves a few writes to the inode and
memory barriers.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
---
mm/filemap.c | 13 -------------
mm/swap_state.c | 4 ----
mm/truncate.c | 1 -
mm/workingset.c | 1 -
4 files changed, 19 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index bd116f63263e..2e68116be4b0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -140,17 +140,6 @@ static void page_cache_delete(struct address_space *mapping,
page->mapping = NULL;
/* Leave page->index set: truncation lookup relies upon it */
-
- if (shadow) {
- mapping->nrexceptional += nr;
- /*
- * Make sure the nrexceptional update is committed before
- * the nrpages update so that final truncate racing
- * with reclaim does not see both counters 0 at the
- * same time and miss a shadow entry.
- */
- smp_wmb();
- }
mapping->nrpages -= nr;
}
@@ -883,8 +872,6 @@ noinline int __add_to_page_cache_locked(struct page *page,
if (xas_error(&xas))
goto unlock;
- if (old)
- mapping->nrexceptional--;
mapping->nrpages++;
/* hugetlb pages do not participate in page cache accounting */
diff --git a/mm/swap_state.c b/mm/swap_state.c
index ee465827420e..85aca8d63aeb 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -160,7 +160,6 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry,
xas_store(&xas, page);
xas_next(&xas);
}
- address_space->nrexceptional -= nr_shadows;
address_space->nrpages += nr;
__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
ADD_CACHE_INFO(add_total, nr);
@@ -199,8 +198,6 @@ void __delete_from_swap_cache(struct page *page,
xas_next(&xas);
}
ClearPageSwapCache(page);
- if (shadow)
- address_space->nrexceptional += nr;
address_space->nrpages -= nr;
__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
ADD_CACHE_INFO(del_total, nr);
@@ -301,7 +298,6 @@ void clear_shadow_from_swap_cache(int type, unsigned long begin,
xas_store(&xas, NULL);
nr_shadows++;
}
- address_space->nrexceptional -= nr_shadows;
xa_unlock_irq(&address_space->i_pages);
/* search the next swapcache until we meet end */
diff --git a/mm/truncate.c b/mm/truncate.c
index 58524aaf67e2..27cf411ae51f 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -40,7 +40,6 @@ static inline void __clear_shadow_entry(struct address_space *mapping,
if (xas_load(&xas) != entry)
return;
xas_store(&xas, NULL);
- mapping->nrexceptional--;
}
static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
diff --git a/mm/workingset.c b/mm/workingset.c
index 975a4d2dd02e..74d5f460e446 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -557,7 +557,6 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
goto out_invalid;
if (WARN_ON_ONCE(node->count != node->nr_values))
goto out_invalid;
- mapping->nrexceptional -= node->nr_values;
xa_delete_node(node, workingset_update_node);
__inc_lruvec_slab_state(node, WORKINGSET_NODERECLAIM);
--
2.28.0
9:44 p.m.
New subject: [PATCH v2 2/4] mm: Stop accounting shadow entries
On Mon, Oct 26, 2020 at 03:18:47PM +0000, Matthew Wilcox (Oracle) wrote:
We no longer need to keep track of how many shadow entries are
present in a mapping. This saves a few writes to the inode and
memory barriers.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
Acked-by: Johannes Weiner <hannes(a)cmpxchg.org>
4:18 p.m.
New subject: [PATCH v2 3/4] dax: Account DAX entries as nrpages
Simplify mapping_needs_writeback() by accounting DAX entries as
pages instead of exceptional entries.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
---
fs/dax.c | 6 +++---
mm/filemap.c | 3 ---
2 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 53ed0ab8c958..a20f2342a9e4 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -525,7 +525,7 @@ static void *grab_mapping_entry(struct xa_state *xas,
dax_disassociate_entry(entry, mapping, false);
xas_store(xas, NULL); /* undo the PMD join */
dax_wake_entry(xas, entry, true);
- mapping->nrexceptional--;
+ mapping->nrpages -= PG_PMD_NR;
entry = NULL;
xas_set(xas, index);
}
@@ -541,7 +541,7 @@ static void *grab_mapping_entry(struct xa_state *xas,
dax_lock_entry(xas, entry);
if (xas_error(xas))
goto out_unlock;
- mapping->nrexceptional++;
+ mapping->nrpages += 1UL << order;
}
out_unlock:
@@ -661,7 +661,7 @@ static int __dax_invalidate_entry(struct address_space *mapping,
goto out;
dax_disassociate_entry(entry, mapping, trunc);
xas_store(&xas, NULL);
- mapping->nrexceptional--;
+ mapping->nrpages -= 1UL << dax_entry_order(entry);
ret = 1;
out:
put_unlocked_entry(&xas, entry);
diff --git a/mm/filemap.c b/mm/filemap.c
index 2e68116be4b0..2214a2c48dd1 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -616,9 +616,6 @@ EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
/* Returns true if writeback might be needed or already in progress. */
static bool mapping_needs_writeback(struct address_space *mapping)
{
- if (dax_mapping(mapping))
- return mapping->nrexceptional;
-
return mapping->nrpages;
}
--
2.28.0
9:46 p.m.
New subject: [PATCH v2 3/4] dax: Account DAX entries as nrpages
On Mon, Oct 26, 2020 at 03:18:48PM +0000, Matthew Wilcox (Oracle) wrote:
Simplify mapping_needs_writeback() by accounting DAX entries as
pages instead of exceptional entries.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
Acked-by: Johannes Weiner <hannes(a)cmpxchg.org>
4:18 p.m.
New subject: [PATCH v2 4/4] mm: Remove nrexceptional from inode
We no longer track anything in nrexceptional, so remove it, saving 8
bytes per inode.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
---
fs/inode.c | 2 +-
include/linux/fs.h | 2 --
2 files changed, 1 insertion(+), 3 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index 9d78c37b00b8..4531358ae97b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -530,7 +530,7 @@ void clear_inode(struct inode *inode)
*/
xa_lock_irq(&inode->i_data.i_pages);
BUG_ON(inode->i_data.nrpages);
- BUG_ON(inode->i_data.nrexceptional);
+ BUG_ON(!mapping_empty(&inode->i_data));
xa_unlock_irq(&inode->i_data.i_pages);
BUG_ON(!list_empty(&inode->i_data.private_list));
BUG_ON(!(inode->i_state & I_FREEING));
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0bd126418bb6..a5d801430040 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -439,7 +439,6 @@ int pagecache_write_end(struct file *, struct address_space *mapping,
* @i_mmap: Tree of private and shared mappings.
* @i_mmap_rwsem: Protects @i_mmap and @i_mmap_writable.
* @nrpages: Number of page entries, protected by the i_pages lock.
- * @nrexceptional: Shadow or DAX entries, protected by the i_pages lock.
* @writeback_index: Writeback starts here.
* @a_ops: Methods.
* @flags: Error bits and flags (AS_*).
@@ -460,7 +459,6 @@ struct address_space {
struct rb_root_cached i_mmap;
struct rw_semaphore i_mmap_rwsem;
unsigned long nrpages;
- unsigned long nrexceptional;
pgoff_t writeback_index;
const struct address_space_operations *a_ops;
unsigned long flags;
--
2.28.0
9:47 p.m.
New subject: [PATCH v2 4/4] mm: Remove nrexceptional from inode
On Mon, Oct 26, 2020 at 03:18:49PM +0000, Matthew Wilcox (Oracle) wrote:
We no longer track anything in nrexceptional, so remove it, saving 8
bytes per inode.
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Tested-by: Vishal Verma <vishal.l.verma(a)intel.com>
Acked-by: Johannes Weiner <hannes(a)cmpxchg.org>
7:43 p.m.
Ping? These patches still apply to next-20210121.
On Mon, Oct 26, 2020 at 03:18:45PM +0000, Matthew Wilcox (Oracle) wrote:
> We actually use nrexceptional for very little these days. It's a minor
> pain to keep in sync with nrpages, but the pain becomes much bigger
> with the THP patches because we don't know how many indices a shadow
> entry occupies. It's easier to just remove it than keep it accurate.
>
> Also, we save 8 bytes per inode which is nothing to sneeze at; on my
> laptop, it would improve shmem_inode_cache from 22 to 23 objects per
> 16kB, and inode_cache from 26 to 27 objects. Combined, that saves
> a megabyte of memory from a combined usage of 25MB for both caches.
> Unfortunately, ext4 doesn't cross a magic boundary, so it doesn't save
> any memory for ext4.
>
> Matthew Wilcox (Oracle) (4):
> mm: Introduce and use mapping_empty
> mm: Stop accounting shadow entries
> dax: Account DAX entries as nrpages
> mm: Remove nrexceptional from inode
>
> fs/block_dev.c | 2 +-
> fs/dax.c | 8 ++++----
> fs/gfs2/glock.c | 3 +--
> fs/inode.c | 2 +-
> include/linux/fs.h | 2 --
> include/linux/pagemap.h | 5 +++++
> mm/filemap.c | 16 ----------------
> mm/swap_state.c | 4 ----
> mm/truncate.c | 19 +++----------------
> mm/workingset.c | 1 -
> 10 files changed, 15 insertions(+), 47 deletions(-)
>
> --
> 2.28.0
>
3:35 a.m.
Ping?
On Thu, Jan 21, 2021 at 06:43:34PM +0000, Matthew Wilcox wrote:
> Ping? These patches still apply to next-20210121.
>
> On Mon, Oct 26, 2020 at 03:18:45PM +0000, Matthew Wilcox (Oracle) wrote:
> > We actually use nrexceptional for very little these days. It's a minor
> > pain to keep in sync with nrpages, but the pain becomes much bigger
> > with the THP patches because we don't know how many indices a shadow
> > entry occupies. It's easier to just remove it than keep it accurate.
> >
> > Also, we save 8 bytes per inode which is nothing to sneeze at; on my
> > laptop, it would improve shmem_inode_cache from 22 to 23 objects per
> > 16kB, and inode_cache from 26 to 27 objects. Combined, that saves
> > a megabyte of memory from a combined usage of 25MB for both caches.
> > Unfortunately, ext4 doesn't cross a magic boundary, so it doesn't save
> > any memory for ext4.
> >
> > Matthew Wilcox (Oracle) (4):
> > mm: Introduce and use mapping_empty
> > mm: Stop accounting shadow entries
> > dax: Account DAX entries as nrpages
> > mm: Remove nrexceptional from inode
> >
> > fs/block_dev.c | 2 +-
> > fs/dax.c | 8 ++++----
> > fs/gfs2/glock.c | 3 +--
> > fs/inode.c | 2 +-
> > include/linux/fs.h | 2 --
> > include/linux/pagemap.h | 5 +++++
> > mm/filemap.c | 16 ----------------
> > mm/swap_state.c | 4 ----
> > mm/truncate.c | 19 +++----------------
> > mm/workingset.c | 1 -
> > 10 files changed, 15 insertions(+), 47 deletions(-)
> >
> > --
> > 2.28.0
> >
>
8:38 p.m.
On Oct 26, 2020, at 9:18 AM, Matthew Wilcox (Oracle)
<willy(a)infradead.org> wrote:
We actually use nrexceptional for very little these days. It's a minor
pain to keep in sync with nrpages, but the pain becomes much bigger
with the THP patches because we don't know how many indices a shadow
entry occupies. It's easier to just remove it than keep it accurate.
Also, we save 8 bytes per inode which is nothing to sneeze at; on my
laptop, it would improve shmem_inode_cache from 22 to 23 objects per
16kB, and inode_cache from 26 to 27 objects. Combined, that saves
a megabyte of memory from a combined usage of 25MB for both caches.
Unfortunately, ext4 doesn't cross a magic boundary, so it doesn't save
any memory for ext4.
Matthew Wilcox (Oracle) (4):
mm: Introduce and use mapping_empty
mm: Stop accounting shadow entries
dax: Account DAX entries as nrpages
mm: Remove nrexceptional from inode
fs/block_dev.c | 2 +-
fs/dax.c | 8 ++++----
fs/gfs2/glock.c | 3 +--
fs/inode.c | 2 +-
include/linux/fs.h | 2 --
include/linux/pagemap.h | 5 +++++
mm/filemap.c | 16 ----------------
mm/swap_state.c | 4 ----
mm/truncate.c | 19 +++----------------
mm/workingset.c | 1 -
10 files changed, 15 insertions(+), 47 deletions(-)
--
2.28.0
Looks good to me.
Reviewed-by: William Kucharski <william.kucharski(a)oracle.com>
436
days inactive
574
days old
12 comments
4 participants
participants (4)
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Matthew Wilcox -
Matthew Wilcox (Oracle)
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William Kucharski