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Date: Thu, 08 Sep 2016 11:07:20 -0700 From: "Huang\, Ying" <ying.huang@...el.com> To: Anshuman Khandual <khandual@...ux.vnet.ibm.com> Cc: "Huang\, Ying" <ying.huang@...el.com>, Andrew Morton <akpm@...ux-foundation.org>, <tim.c.chen@...el.com>, <dave.hansen@...el.com>, <andi.kleen@...el.com>, <aaron.lu@...el.com>, <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>, Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>, Minchan Kim <minchan@...nel.org>, Rik van Riel <riel@...hat.com> Subject: Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP size on x86_64 Anshuman Khandual <khandual@...ux.vnet.ibm.com> writes: > On 09/07/2016 10:16 PM, Huang, Ying wrote: >> From: Huang Ying <ying.huang@...el.com> >> >> In this patch, the size of the swap cluster is changed to that of the >> THP (Transparent Huge Page) on x86_64 architecture (512). This is for >> the THP swap support on x86_64. Where one swap cluster will be used to >> hold the contents of each THP swapped out. And some information of the >> swapped out THP (such as compound map count) will be recorded in the >> swap_cluster_info data structure. >> >> For other architectures which want THP swap support, THP_SWAP_CLUSTER >> need to be selected in the Kconfig file for the architecture. >> >> In effect, this will enlarge swap cluster size by 2 times on x86_64. >> Which may make it harder to find a free cluster when the swap space >> becomes fragmented. So that, this may reduce the continuous swap space >> allocation and sequential write in theory. The performance test in 0day >> shows no regressions caused by this. > > This patch needs to be split into two separate ones > > (1) Add THP_SWAP_CLUSTER config option > (2) Enable CONFIG_THP_SWAP_CLUSTER for X86_64 > > The first patch should explain the proposal and the second patch > should have 86_64 arch specific details, regressions etc as already > been explained in the commit message. The code change and possible issues is not x86_64 specific, but general for all architectures where the config option is enabled. If so, the second patch becomes 1 line kconfig change and no much to be said in patch description. Does it deserve a separate patch? Best Regards, Huang, Ying
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