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Fri, 10 Jan 2020 21:34:46 +0000 (UTC) Received: by mail-pl1-f194.google.com with SMTP id x17so1331872pln.1 for ; Fri, 10 Jan 2020 13:34:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=//Vec5skQW+H9IPGRTNbLtqR3goYkBV9ehrKBDaBk60=; b=rURmhW8wIF5KaQsftvbrXK/WNqEug54J5oUNqc7D2y8i0VNxKhfqtIIWkeKS+rI+rf ukFURwW9nBJzL2fIW5hQ/oFXNOgNWzwsvTw/Zoa4OQKmQ2U9pcNQZVzs+vMEOjHz8agB Yl76iCX6lKPXezdEACjEkV+oZgyKT5n5CoJNlvEbBDcVwI+u0Ol5QPl2AcmNyY7dzZIa 8CC3O7wtMjWAPrJtm5srhBkqvguebPYp7vKuCR98SQeUQEutaxAfumTwgQe72TDSFy8d /0cIAWs2gl26s6vbbkPuKVU9i8VipkyIFZ9F7IE+gBRXE4s3I1JAEm0H7GnfYE2U969x VhUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; bh=//Vec5skQW+H9IPGRTNbLtqR3goYkBV9ehrKBDaBk60=; 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And the only way to get around that is to either: * use LD_PRELOAD; or * patch the kernel with something like UKSM or PKSM. (i skip ptrace can of worms here intentionally) To overcome this restriction, lets employ a new remote madvise API. This can be used by some small userspace helper daemon that will do auto-KSM job for us. I think of two major consumers of remote KSM hints: * hosts, that run containers, especially similar ones and especially in a trusted environment, sharing the same runtime like Node.js; * heavy applications, that can be run in multiple instances, not limited to opensource ones like Firefox, but also those that cannot b= e modified since they are binary-only and, maybe, statically linked. Speaking of statistics, more numbers can be found in the very first submission, that is related to this one [1]. For my current setup with two Firefox instances I get 100 to 200 MiB saved for the second instance depending on the amount of tabs. 1 FF instance with 15 tabs: $ echo "$(cat /sys/kernel/mm/ksm/pages_sharing) * 4 / 1024" | bc 410 2 FF instances, second one has 12 tabs (all the tabs are different): $ echo "$(cat /sys/kernel/mm/ksm/pages_sharing) * 4 / 1024" | bc 592 At the very moment I do not have specific numbers for containerised workload, but those should be comparable in case the containers share similar/same runtime. [1] https://lore.kernel.org/patchwork/patch/1012142/ Signed-off-by: Oleksandr Natalenko Signed-off-by: Minchan Kim --- mm/madvise.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index eb42b2b7f49b..3aa9aec6bfd9 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1000,6 +1000,8 @@ process_madvise_behavior_valid(int behavior) switch (behavior) { case MADV_COLD: case MADV_PAGEOUT: + case MADV_MERGEABLE: + case MADV_UNMERGEABLE: return true; default: return false; --=20 2.25.0.rc1.283.g88dfdc4193-goog