The patch titled
readahead: trigger mmap sequential readahead on PG_readahead
has been removed from the -mm tree. Its filename was
readahead-trigger-mmap-sequential-readahead-on-pg_readahead.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: readahead: trigger mmap sequential readahead on PG_readahead
From: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Previously the mmap sequential readahead is triggered by updating
ra->prev_pos on each page fault and compare it with current page offset.
It costs dirtying the cache line on each _minor_ page fault. So remove
the ra->prev_pos recording, and instead tag PG_readahead to trigger the
possible sequential readahead. It's not only more simple, but also will
work more reliably and reduce cache line bouncing on concurrent page
faults on shared struct file.
In the mosbench exim benchmark which does multi-threaded page faults on
shared struct file, the ra->mmap_miss and ra->prev_pos updates are found
to cause excessive cache line bouncing on tmpfs, which actually disabled
readahead totally (shmem_backing_dev_info.ra_pages == 0).
So remove the ra->prev_pos recording, and instead tag PG_readahead to
trigger the possible sequential readahead. It's not only more simple, but
also will work more reliably on concurrent reads on shared struct file.
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Tested-by: Tim Chen <tim.c.chen@xxxxxxxxx>
Reported-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff -puN mm/filemap.c~readahead-trigger-mmap-sequential-readahead-on-pg_readahead mm/filemap.c
--- a/mm/filemap.c~readahead-trigger-mmap-sequential-readahead-on-pg_readahead
+++ a/mm/filemap.c
@@ -1559,8 +1559,7 @@ static void do_sync_mmap_readahead(struc
if (!ra->ra_pages)
return;
- if (VM_SequentialReadHint(vma) ||
- offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
+ if (VM_SequentialReadHint(vma)) {
page_cache_sync_readahead(mapping, ra, file, offset,
ra->ra_pages);
return;
@@ -1583,7 +1582,7 @@ static void do_sync_mmap_readahead(struc
ra_pages = max_sane_readahead(ra->ra_pages);
ra->start = max_t(long, 0, offset - ra_pages / 2);
ra->size = ra_pages;
- ra->async_size = 0;
+ ra->async_size = ra_pages / 4;
ra_submit(ra, mapping, file);
}
@@ -1689,7 +1688,6 @@ retry_find:
return VM_FAULT_SIGBUS;
}
- ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
vmf->page = page;
return ret | VM_FAULT_LOCKED;
_
Patches currently in -mm which might be from fengguang.wu@xxxxxxxxx are
origin.patch
writeback-pass-writeback_control-down-to-move_expired_inodes.patch
writeback-introduce-writeback_controlinodes_cleaned.patch
writeback-try-more-writeback-as-long-as-something-was-written.patch
writeback-the-kupdate-expire-timestamp-should-be-a-moving-target.patch
writeback-sync-expired-inodes-first-in-background-writeback.patch
writeback-sync-expired-inodes-first-in-background-writeback-fix.patch
writeback-refill-b_io-iff-empty.patch
writeback-split-inode_wb_list_lock-into-bdi_writebacklist_lock.patch
writeback-split-inode_wb_list_lock-into-bdi_writebacklist_lock-fix.patch
writeback-split-inode_wb_list_lock-into-bdi_writebacklist_lock-fix-fix.patch
writeback-split-inode_wb_list_lock-into-bdi_writebacklist_lock-fix-fix-fix.patch
writeback-elevate-queue_io-into-wb_writeback.patch
writeback-introduce-wbctagged_sync-for-the-wb_sync_none-sync-stage.patch
writeback-update-dirtied_when-for-synced-inode-to-prevent-livelock.patch
writeback-avoid-extra-sync-work-at-enqueue-time.patch
getdelays-show-average-cpu-io-swap-reclaim-delays.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
