From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hugh Dickins Subject: Re: [PATCH] mm: vmpressure: fix scan window after SWAP_CLUSTER_MAX increase Date: Wed, 21 Oct 2015 13:05:53 -0700 (PDT) Message-ID: References: <1445278381-21033-1-git-send-email-hannes@cmpxchg.org> <20151021193852.GA13511@cmpxchg.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version:content-type; bh=X4B1i4lJzk7TKq4jKBkyEPCXNYWrAtw1jDgkZ1LS40o=; b=oeo9a7+I3e1/yTj9qCdVQof5D8jKQ9/bYEVmKYXL5/3vGZXMLxnc57DfLj4GHN4crk szigqPZdo1BgBr4hYFjH/AoIIjSY5ZKylPQKr20yeuOq4JdQRTomrGvs2Sc/2WArETOK E+Y9FmSFtb+Fzsbf2r0F7OL7byr3uRXzVgK1o9Q+c/DuU+bCmhbS44xetAqJjH0lriSh qZ8dThl2sG7aTIN2TLWap37hfcKqvtNwJEP1uKDUQVB9wfXAcllE0Yc4fgCAl1PpPf3p IZhZjtK76qwrXbpAbd2r8Z98yeLRrsl+NH5yl5neZKDu0e40FcMnsjUL6AgwAeos08Iy t7sQ== In-Reply-To: <20151021193852.GA13511@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: TEXT/PLAIN; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Andrew Morton , Vladimir Davydov , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Wed, 21 Oct 2015, Johannes Weiner wrote: > On Mon, Oct 19, 2015 at 02:13:01PM -0400, Johannes Weiner wrote: > > mm-increase-swap_cluster_max-to-batch-tlb-flushes.patch changed > > SWAP_CLUSTER_MAX from 32 pages to 256 pages, inadvertantly switching > > the scan window for vmpressure detection from 2MB to 16MB. Revert. > > > > Signed-off-by: Johannes Weiner > > --- > > mm/vmpressure.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/vmpressure.c b/mm/vmpressure.c > > index c5afd57..74f206b 100644 > > --- a/mm/vmpressure.c > > +++ b/mm/vmpressure.c > > @@ -38,7 +38,7 @@ > > * TODO: Make the window size depend on machine size, as we do for vmstat > > * thresholds. Currently we set it to 512 pages (2MB for 4KB pages). > > */ > > -static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16; > > +static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX; > > Argh, Mel's patch sets SWAP_CLUSTER_MAX to 256, so this should be > SWAP_CLUSTER_MAX * 2 to retain the 512 pages scan window. > > Andrew could you please update this fix in-place? Otherwise I'll > resend a corrected version. > > Thanks, and sorry about that. I don't understand why "SWAP_CLUSTER_MAX * 2" is thought better than "512". Retaining a level of obscurity, that just bit us twice, is a good thing? Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org