Messages in this thread | | | Date | Thu, 16 Oct 2014 14:48:42 +0900 | From | Heesub Shin <> | Subject | Re: [PATCH] mm/zbud: init user ops only when it is needed |
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Hello,
On 10/16/2014 05:17 AM, Andrew Morton wrote: > On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin <heesub.shin@samsung.com> wrote: > >> When zbud is initialized through the zpool wrapper, pool->ops which >> points to user-defined operations is always set regardless of whether it >> is specified from the upper layer. This causes zbud_reclaim_page() to >> iterate its loop for evicting pool pages out without any gain. >> >> This patch sets the user-defined ops only when it is needed, so that >> zbud_reclaim_page() can bail out the reclamation loop earlier if there >> is no user-defined operations specified. > > Which callsite is calling zbud_zpool_create(..., NULL)?
Currently nowhere. zswap is the only user of zbud and always passes a pointer to user-defined operation on pool creation. In addition, there may be less possibility that pool shrinking is requested by users who did not provide the user-defined ops. So, we may not need to worry much about what I wrote in the changelog. However, it is definitely weird to pass an argument, zpool_ops, which even will not be referenced by zbud_zpool_create(). Above all, it would be more useful to avoid the possibility in the future rather than just ignoring it.
regards, heesub
> >> ... >> --- a/mm/zbud.c >> +++ b/mm/zbud.c >> @@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = { >> >> static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops) >> { >> - return zbud_create_pool(gfp, &zbud_zpool_ops); >> + return zbud_create_pool(gfp, zpool_ops ? &zbud_zpool_ops : NULL); >> } >> >> static void zbud_zpool_destroy(void *pool) > >
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