From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f169.google.com (mail-ob0-f169.google.com [209.85.214.169]) by kanga.kvack.org (Postfix) with ESMTP id 3952F830B6 for ; Thu, 18 Feb 2016 20:19:58 -0500 (EST) Received: by mail-ob0-f169.google.com with SMTP id xk3so95421630obc.2 for ; Thu, 18 Feb 2016 17:19:58 -0800 (PST) Received: from mail-ob0-x236.google.com (mail-ob0-x236.google.com. [2607:f8b0:4003:c01::236]) by mx.google.com with ESMTPS id oi10si2356053oeb.67.2016.02.18.17.19.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Feb 2016 17:19:57 -0800 (PST) Received: by mail-ob0-x236.google.com with SMTP id xk3so95421424obc.2 for ; Thu, 18 Feb 2016 17:19:57 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20160218101909.GB503@swordfish> References: <1455764556-13979-1-git-send-email-sergey.senozhatsky@gmail.com> <1455764556-13979-4-git-send-email-sergey.senozhatsky@gmail.com> <20160218095536.GA503@swordfish> <20160218101909.GB503@swordfish> Date: Fri, 19 Feb 2016 10:19:57 +0900 Message-ID: Subject: Re: [RFC PATCH 3/3] mm/zsmalloc: change ZS_MAX_PAGES_PER_ZSPAGE From: Joonsoo Kim Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Sergey Senozhatsky Cc: Andrew Morton , Minchan Kim , Linux Memory Management List , LKML , Sergey Senozhatsky 2016-02-18 19:19 GMT+09:00 Sergey Senozhatsky : > On (02/18/16 18:55), Sergey Senozhatsky wrote: >> > There is a reason that it is order of 2. Increasing ZS_MAX_PAGES_PER_ZSPAGE >> > is related to ZS_MIN_ALLOC_SIZE. If we don't have enough OBJ_INDEX_BITS, >> > ZS_MIN_ALLOC_SIZE would be increase and it causes regression on some >> > system. >> >> Thanks! >> >> do you mean PHYSMEM_BITS != BITS_PER_LONG systems? PAE/LPAE? isn't it >> the case that on those systems ZS_MIN_ALLOC_SIZE already bigger than 32? Indeed. > I mean, yes, there are ZS_ALIGN requirements that I completely ignored, > thanks for pointing that out. > > just saying, not insisting on anything, theoretically, trading 32 bit size > objects in exchange of reducing a much bigger memory wastage is sort of > interesting. zram stores objects bigger than 3072 as huge objects, leaving I'm also just saying. :) On the above example system which already uses 128 byte min class, your change makes it to 160 or 192. It could make a more trouble than you thought. > 4096-3072 bytes unused, and it'll take 4096-3072/32 = 4000 32 bit objects > to beat that single 'bad' compression object in storing inefficiency... Where does 4096-3072/32 calculation comes from? I'm not familiar to recent change on zsmalloc such as huge class so can't understand this calculation. > well, patches 0001/0002 are trying to address this a bit, but the biggest > problem is still there: we have too many ->huge classes and they are a bit > far from good. Agreed. And I agree your patchset, too. Anyway, could you answer my other questions on original reply? Thanks. -- 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