lkml.org 
[lkml]   [2017]   [Apr]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4 2/4] zram: implement deduplication in zram
On (04/26/17 09:52), js1304@gmail.com wrote:
[..]
> +struct zram_hash {
> + spinlock_t lock;
> + struct rb_root rb_root;
> };

just a note.

we can easily have N CPUs spinning on ->lock for __zram_dedup_get() lookup,
which can invole a potentially slow zcomp_decompress() [zlib, for example,
with 64k pages] and memcmp(). the larger PAGE_SHIFT is, the more serialized
IOs become. in theory, at least.

CPU0 CPU1 ... CPUN

__zram_bvec_write() __zram_bvec_write() __zram_bvec_write()
zram_dedup_find() zram_dedup_find() zram_dedup_find()
spin_lock(&hash->lock);
spin_lock(&hash->lock); spin_lock(&hash->lock);
__zram_dedup_get()
zcomp_decompress()
...


so may be there is a way to use read-write lock instead on spinlock for hash
and reduce write/read IO serialization.

-ss

\
 
 \ /
  Last update: 2017-04-26 06:29    [W:0.114 / U:3.380 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site