From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 519BAC433DB for ; Thu, 14 Jan 2021 18:43:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D2E6023B46 for ; Thu, 14 Jan 2021 18:43:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D2E6023B46 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1231D8D0106; Thu, 14 Jan 2021 13:43:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0AC458D00F0; Thu, 14 Jan 2021 13:43:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E67408D0106; Thu, 14 Jan 2021 13:43:25 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0051.hostedemail.com [216.40.44.51]) by kanga.kvack.org (Postfix) with ESMTP id CD74C8D00F0 for ; Thu, 14 Jan 2021 13:43:25 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 99F33824556B for ; Thu, 14 Jan 2021 18:43:25 +0000 (UTC) X-FDA: 77705253570.19.crook77_0311b6b27528 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin19.hostedemail.com (Postfix) with ESMTP id 75B6C1ACC30 for ; Thu, 14 Jan 2021 18:43:25 +0000 (UTC) X-HE-Tag: crook77_0311b6b27528 X-Filterd-Recvd-Size: 4888 Received: from mail-lj1-f179.google.com (mail-lj1-f179.google.com [209.85.208.179]) by imf04.hostedemail.com (Postfix) with ESMTP for ; Thu, 14 Jan 2021 18:43:24 +0000 (UTC) Received: by mail-lj1-f179.google.com with SMTP id w26so7629997ljo.4 for ; Thu, 14 Jan 2021 10:43:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Lxa7NZ97f44YwUR9/BBXmGhDhXrkOtkw4W6gk+s0s54=; b=R8ksmBtly6F+Mp4m8DdAqed9RC3UDV/QkrtFAP7dJmvnSXdjqiRgun7BTUXOkvz7Jd eUVG4KAj5JxBaNb4v+v/RRyOVQ/zip/PBxkEjFZjZG+8o5MF1ghQ4t4PQd+ZBmip7Aw2 /C+6hXjGcNVYN1l1LD9vTqodQ/QFlDGvOuh5W9F9HTSlNA9IVQCdP6atpZ7CUftbJW5D Qi2W8KxkabZJv9iMg1zVaarhLrrosJnY5dNRJttSb98wAOfs3jJNClYau5+vtERS7Xo/ 5I+N7nIJ7v8n4Db6KsvJ+RzWunLdl7ael7ZSBJ79xkVRX7si74gGnJ9zsB0Ds32TMWe2 SuAA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Lxa7NZ97f44YwUR9/BBXmGhDhXrkOtkw4W6gk+s0s54=; b=IYqne9NDntO2eVC2Ebkm5zJUioWmSQWOF1C97XvzFmK9ABmv06wBQeD7I7T8rZwBAh plZ0xq8EIFTNfx0FvIC5PjWaPYazgmtDVxsBcnJiuy9yrhdy2XZ4UiQdzHz9yd4LciLi RqU+vHfUqPnD9RIGS915YnPAHrZflf9MTwKrl3yPaAttboZHelCu8hm9Kp/K80vEXg8i FNR//XstvcUgVKY96NIcIHvTPKyFdHJQiI3KGpeVe77bbdY9wCG3+Cy0pVn0AxHuabvU +Lkmf5v3WXUV6o1YMVNqKehg6wEfkf72bt51BnDWVTcNch9NizNaTZgPCxJ/ulaE0xd4 KoRg== X-Gm-Message-State: AOAM532cXaqC3lX0dvETIy6MnI9PyEpGq7+JuVNaQtUvyeEC4ydTu4j/ jC7zP9jslwDBhQmxKb70JtKPGupRrVUl5VSIZruu8A== X-Google-Smtp-Source: ABdhPJyBqhcGfPOjBO8ihJxudv5KJnOr4En5Y0XlGHU2TWeyoaPbf2G0ggVjrpk+UZAQUftwne2q3GZqrnV4A+RONVk= X-Received: by 2002:a2e:b0d3:: with SMTP id g19mr3811862ljl.279.1610649803223; Thu, 14 Jan 2021 10:43:23 -0800 (PST) MIME-Version: 1.0 References: <1608894171-54174-1-git-send-email-tiantao6@hisilicon.com> <1608894171-54174-2-git-send-email-tiantao6@hisilicon.com> In-Reply-To: From: Shakeel Butt Date: Thu, 14 Jan 2021 10:43:12 -0800 Message-ID: Subject: Re: [RFC mm/zswap 1/2] mm/zswap: add the flag can_sleep_mapped To: Minchan Kim Cc: Tian Tao , Seth Jennings , Dan Streetman , Vitaly Wool , Andrew Morton , Barry Song , Linux MM , Sergey Senozhatsky Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 14, 2021 at 10:29 AM Minchan Kim wrote: > > On Fri, Dec 25, 2020 at 07:02:50PM +0800, Tian Tao wrote: > > add a flag to zpool, named is "can_sleep_mapped", and have it set true > > for zbud/z3fold, set false for zsmalloc. Then zswap could go the current > > path if the flag is true; and if it's false, copy data from src to a > > temporary buffer, then unmap the handle, take the mutex, process the > > buffer instead of src to avoid sleeping function called from atomic > > context. > > > > Signed-off-by: Tian Tao > > --- > > include/linux/zpool.h | 3 +++ > > mm/zpool.c | 13 +++++++++++++ > > mm/zswap.c | 50 +++++++++++++++++++++++++++++++++++++++++++++----- > > 3 files changed, 61 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/zpool.h b/include/linux/zpool.h > > index 51bf430..e899701 100644 > > --- a/include/linux/zpool.h > > +++ b/include/linux/zpool.h > > @@ -73,6 +73,7 @@ u64 zpool_get_total_size(struct zpool *pool); > > * @malloc: allocate mem from a pool. > > * @free: free mem from a pool. > > * @shrink: shrink the pool. > > + * @sleep_mapped: whether zpool driver can sleep during map. > > I don't think it's a good idea. It just breaks zpool abstraction > in that it exposes internal implementation to user to avoid issue > zswap recently introduced. It also conflicts zpool_map_handle's > semantic. > > Rather than introducing another break in zpool due to the new > zswap feature recenlty introduced, zswap could introduce > CONFIG_ZSWAP_HW_COMPRESSOR. Once it's configured, zsmalloc could > be disabled. And with disabling CONFIG_ZSWAP_HW_COMPRESSOR, zswap > doesn't need to make any bounce buffer copy so that no existing > zsmalloc user will see performance regression. > I agree with Minchan. There is no reason to add extra overhead for configurations where there is no hardware available.