Messages in this thread Patch in this message | | | Date | Tue, 26 Jun 2012 11:12:22 +0400 | From | Glauber Costa <> | Subject | Re: [PATCH 02/11] memcg: Reclaim when more than one page needed. |
| |
> >> + * retries >> + */ >> +#define NR_PAGES_TO_RETRY 2 >> + > > Should be 1 << PAGE_ALLOC_COSTLY_ORDER? Where does this number come from? > The changelog doesn't specify.
Hocko complained about that, and I changed. Where the number comes from, is stated in the comments: it is a number small enough to have high changes of had been freed by the previous reclaim, and yet around the number of pages of a kernel allocation.
Of course there are allocations for nr_pages > 2. But 2 will already service the stack most of the time, and most of the slab caches.
>> static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, >> - unsigned int nr_pages, bool oom_check) >> + unsigned int nr_pages, unsigned int min_pages, >> + bool oom_check) >> { >> unsigned long csize = nr_pages * PAGE_SIZE; >> struct mem_cgroup *mem_over_limit; >> @@ -2182,18 +2190,18 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, >> } else >> mem_over_limit = mem_cgroup_from_res_counter(fail_res, res); >> /* >> - * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch >> - * of regular pages (CHARGE_BATCH), or a single regular page (1). >> - * >> * Never reclaim on behalf of optional batching, retry with a >> * single page instead. >> */ >> - if (nr_pages == CHARGE_BATCH) >> + if (nr_pages > min_pages) >> return CHARGE_RETRY; >> >> if (!(gfp_mask & __GFP_WAIT)) >> return CHARGE_WOULDBLOCK; >> >> + if (gfp_mask & __GFP_NORETRY) >> + return CHARGE_NOMEM; >> + >> ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags); >> if (mem_cgroup_margin(mem_over_limit) >= nr_pages) >> return CHARGE_RETRY; >> @@ -2206,7 +2214,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, >> * unlikely to succeed so close to the limit, and we fall back >> * to regular pages anyway in case of failure. >> */ >> - if (nr_pages == 1 && ret) >> + if (nr_pages <= NR_PAGES_TO_RETRY && ret) >> return CHARGE_RETRY; >> >> /* >> @@ -2341,7 +2349,8 @@ again: >> nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES; >> } >> >> - ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, oom_check); >> + ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, nr_pages, >> + oom_check); >> switch (ret) { >> case CHARGE_OK: >> break;
| |