On Mon, Sep 03, 2012 at 07:46:31PM +0800, Shaohua Li wrote: > On Mon, Sep 03, 2012 at 05:32:45PM +0900, Minchan Kim wrote: > > Don't we need initialization? > > > > diff --git a/mm/rmap.c b/mm/rmap.c > > index 0f3b7cd..c0f3221 100644 > > --- a/mm/rmap.c > > +++ b/mm/rmap.c > > @@ -416,6 +416,9 @@ static void anon_vma_ctor(void *data) > > > > mutex_init(&anon_vma->mutex); > > atomic_set(&anon_vma->refcount, 0); > > +#ifdef CONFIG_SWAP > > + atomic_set(&anon_vma->swapra_miss, 0); > > +#endif > > INIT_LIST_HEAD(&anon_vma->head); > > } > > Sorry about this silly problem. I'm wondering why I didn't notice it, maybe > because only tested random swap after move swapra_miss to anon_vma. > > > Subject: swap: add a simple random read swapin detection > > The swapin readahead does a blind readahead regardless if the swapin is > sequential. This is ok for harddisk and random read, because read big size has > no penality in harddisk, and if the readahead pages are garbage, they can be > reclaimed fastly. But for SSD, big size read is more expensive than small size > read. If readahead pages are garbage, such readahead only has overhead. > > This patch addes a simple random read detection like what file mmap readahead > does. If random read is detected, swapin readahead will be skipped. This > improves a lot for a swap workload with random IO in a fast SSD. > > I run anonymous mmap write micro benchmark, which will triger swapin/swapout. > runtime changes with path > randwrite harddisk -38.7% > seqwrite harddisk -1.1% > randwrite SSD -46.9% > seqwrite SSD +0.3% > > For both harddisk and SSD, the randwrite swap workload run time is reduced > significant. sequential write swap workload hasn't chanage. > > Interesting is the randwrite harddisk test is improved too. This might be > because swapin readahead need allocate extra memory, which further tights > memory pressure, so more swapout/swapin. > > This patch depends on readahead-fault-retry-breaks-mmap-file-read-random-detection.patch > > V2->V3: > move swapra_miss to 'struct anon_vma' as suggested by Konstantin. > > V1->V2: > 1. Move the swap readahead accounting to separate functions as suggested by Riel. > 2. Enable the logic only with CONFIG_SWAP enabled as suggested by Minchan. > > Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx> > Acked-by: Rik van Riel <riel@xxxxxxxxxx> Reviewed-by: Minchan Kim <minchan@xxxxxxxxxx> Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>