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Date: Tue, 5 Jan 2021 16:07:48 -0800 From: Mike Kravetz <mike.kravetz@...cle.com> To: Muchun Song <songmuchun@...edance.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, Andi Kleen <ak@...ux.intel.com>, mhocko@...e.cz, Linux Memory Management List <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [External] Re: [PATCH 4/6] mm: hugetlb: add return -EAGAIN for dissolve_free_huge_page On 1/4/21 7:46 PM, Muchun Song wrote: > On Tue, Jan 5, 2021 at 11:14 AM Muchun Song <songmuchun@...edance.com> wrote: >> >> On Tue, Jan 5, 2021 at 9:33 AM Mike Kravetz <mike.kravetz@...cle.com> wrote: >>> >>> On 1/3/21 10:58 PM, Muchun Song wrote: >>>> When dissolve_free_huge_page() races with __free_huge_page(), we can >>>> do a retry. Because the race window is small. >>> >>> In general, I agree that the race window is small. However, worst case >>> would be if the freeing of the page is put on a work queue. Is it acceptable >>> to keep retrying in that case? In addition, the 'Free some vmemmap' series >>> may slow the free_huge_page path even more. >> >> I also consider the 'Free some vmemmap' series case. In my next >> version series, I will flush the work before dissolve_free_huge_page >> returns when encountering this race. So the retry is acceptable. >> Right? > > Hi Mike, > > How about flushing the @free_hpage_work when > encountering this race? Flushing should be fine. The more I think about it, the more I think spinning to retry is not going to be an issue. Why? As you mentioned the race window is quite small. It just makes me a bit nervous to retry in a tight loop. -- Mike Kravetz
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