From patchwork Fri Jan 26 21:30:33 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 13533329 Received: from mail-io1-f45.google.com (mail-io1-f45.google.com [209.85.166.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3D91B24B20 for ; Fri, 26 Jan 2024 21:38:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.45 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706305118; cv=none; b=gxBUPUZT730qo/KBsNgaHdJgPhAQdmkAAd4WbD4idEAZavsZR4/kItVc40esUkU76Vy2RfseYPA66OjWoS9PdqAPhn10+6nN+DhEUf8sm6c/7HUVxZl5gyjVmsKYQnqh/ijE6+6JoLYERy7eY7XOw6MGZoJMTsbtZJRqnTCqZFU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706305118; c=relaxed/simple; bh=oNSRfvL538GzIBzKBlHszo9PbeR+CDrnExjMEyUELH0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=b742Q6IRqRK6oXSDeYZYuwqT3Ulj9BX0hcSsJ8uxlrlwXc60X8o15mlw0Mv6CoTDNglt5zjqO4hnGbx1F0j7DEcw1bOlWQXNhkAn2zoI6Kb7/siFbV80jQKHKfT8O8TNd8GrDGFTYoWgCZOR1jfV8wEpu5JJLiSbvlnzDGSumrY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk; spf=pass smtp.mailfrom=kernel.dk; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b=nZOB0RmY; arc=none smtp.client-ip=209.85.166.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.dk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b="nZOB0RmY" Received: by mail-io1-f45.google.com with SMTP id ca18e2360f4ac-7bbdd28a52aso13042939f.1 for ; Fri, 26 Jan 2024 13:38:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1706305115; x=1706909915; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=FDk0YsdpBtyFP4o00bqufxnHQRLTRO82Ylw8HFnti3A=; b=nZOB0RmYGD5oHxbVwH9sBWdc0CUvn+f/nSX90w9py1KetDtxtwEctmRoIyGyDDgwp1 pTpnR3ZL/XGJr79wghbOWAKuLhVGtw9YVVjIzJ1qsnrNIv3e2w85pXVMvLzoV088WR0s l/wdE1YIGci4ugZ5N+pytdVNCaS/KM4PS+FJhBQ11dZqsGgxIBz4OoKnrhOv4izBrqEa FRsNutyYAKe6C8TgkpFl1hRcG+1WthiXXA4xqEbWJJIFCtebkB8/rA1rZ9lyUbVw6A5+ ZIbHlePw8raQ+3xMDuEJZe5sQ6tbmhHzUYS0aMVDqS5xc6eJwZD9P0ABKccDRJLy/UQv QkGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706305115; x=1706909915; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=FDk0YsdpBtyFP4o00bqufxnHQRLTRO82Ylw8HFnti3A=; b=xIT4PEub950FoF09eAHN4fOjR0XK7riSMtzcn553Ls0o7jUuH2SGDwjE3iwjNyy7hi o6yTe2L9ua3duUGoPggHEeAAQEVf2UW6ODznsJ75ZHzpYdN4KSsMU9C7R4rTVaXJvrRr GwGowX3onN4pky/HxBblVn+e9Froa+LeDVwf+qh8HQcqTFntfK4PeWtLppqse2fvDzeG AEfxIltiXirrvjrVjyMFyj3/mJYR0poObac0s8Gx53iFY3HfcK6EY9S4wta7IIgEGi/H GzlzjSnJ5RCW4U5oFa43oJ6qzbJJrqFHhHeVZV3P1QBWErnbdPerw2Sdr23uW+th7LAY EXAw== X-Gm-Message-State: AOJu0Ywo+eh/m/Tn3SEy2oYLXb7pyL7YdbRK0iDvmvF4OtkAKqnY06eD XpxG8mM6bcWbXqiBJVjwe0ykbSNUwrCVrZUFPmkGHtiDKYm0Hqk2s6nskBx5nozo9GgJvAtwYiC O8No= X-Google-Smtp-Source: AGHT+IHcj086MUhPccEVdsQq+xVIwzCPEwCbonbkYnVWX9Un4tK1Wf2VKMwjuz8FSwanTQtz8K6rRQ== X-Received: by 2002:a5d:9c57:0:b0:7bf:b770:d4ed with SMTP id 23-20020a5d9c57000000b007bfb770d4edmr904269iof.0.1706305114854; Fri, 26 Jan 2024 13:38:34 -0800 (PST) Received: from localhost.localdomain ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id b4-20020a029a04000000b0046f34484578sm471788jal.126.2024.01.26.13.38.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jan 2024 13:38:33 -0800 (PST) From: Jens Axboe To: linux-block@vger.kernel.org Cc: Jens Axboe , Johannes Thumshirn Subject: [PATCH 3/4] block: cache current nsec time in struct blk_plug Date: Fri, 26 Jan 2024 14:30:33 -0700 Message-ID: <20240126213827.2757115-4-axboe@kernel.dk> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240126213827.2757115-1-axboe@kernel.dk> References: <20240126213827.2757115-1-axboe@kernel.dk> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Querying the current time is the most costly thing we do in the block layer per IO, and depending on kernel config settings, we may do it many times per IO. None of the callers actually need nsec granularity. Take advantage of that by caching the current time in the plug, with the assumption here being that any time checking will be temporally close enough that the slight loss of precision doesn't matter. If the block plug gets flushed, eg on preempt or schedule out, then we invalidate the cached clock. On a basic peak IOPS test case with iostats enabled, this changes the performance from: IOPS=108.41M, BW=52.93GiB/s, IOS/call=31/31 IOPS=108.43M, BW=52.94GiB/s, IOS/call=32/32 IOPS=108.29M, BW=52.88GiB/s, IOS/call=31/32 IOPS=108.35M, BW=52.91GiB/s, IOS/call=32/32 IOPS=108.42M, BW=52.94GiB/s, IOS/call=31/31 IOPS=108.40M, BW=52.93GiB/s, IOS/call=32/32 IOPS=108.31M, BW=52.89GiB/s, IOS/call=32/31 to IOPS=118.79M, BW=58.00GiB/s, IOS/call=31/32 IOPS=118.62M, BW=57.92GiB/s, IOS/call=31/31 IOPS=118.80M, BW=58.01GiB/s, IOS/call=32/31 IOPS=118.78M, BW=58.00GiB/s, IOS/call=32/32 IOPS=118.69M, BW=57.95GiB/s, IOS/call=32/31 IOPS=118.62M, BW=57.92GiB/s, IOS/call=32/31 IOPS=118.63M, BW=57.92GiB/s, IOS/call=31/32 which is more than a 9% improvement in performance. Looking at perf diff, we can see a huge reduction in time overhead: 10.55% -9.88% [kernel.vmlinux] [k] read_tsc 1.31% -1.22% [kernel.vmlinux] [k] ktime_get Note that since this relies on blk_plug for the caching, it's only applicable to the issue side. But this is where most of the time calls happen anyway. On the completion side, cached time stamping is done with struct io_comp patch, as long as the driver supports it. It's also worth noting that the above testing doesn't enable any of the higher cost CPU items on the block layer side, like wbt, cgroups, iocost, etc, which all would add additional time querying and hence overhead. IOW, results would likely look even better in comparison with those enabled, as distros would do. Reviewed-by: Johannes Thumshirn Signed-off-by: Jens Axboe --- block/blk-core.c | 1 + block/blk.h | 14 +++++++++++++- include/linux/blkdev.h | 1 + 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/block/blk-core.c b/block/blk-core.c index 11342af420d0..cc4db4d92c75 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1073,6 +1073,7 @@ void blk_start_plug_nr_ios(struct blk_plug *plug, unsigned short nr_ios) if (tsk->plug) return; + plug->cur_ktime = 0; plug->mq_list = NULL; plug->cached_rq = NULL; plug->nr_ios = min_t(unsigned short, nr_ios, BLK_MAX_REQUEST_COUNT); diff --git a/block/blk.h b/block/blk.h index 79ae533cdf02..14bbc4b780f2 100644 --- a/block/blk.h +++ b/block/blk.h @@ -519,7 +519,19 @@ static inline int req_ref_read(struct request *req) static inline u64 blk_time_get_ns(void) { - return ktime_get_ns(); + struct blk_plug *plug = current->plug; + + if (!plug) + return ktime_get_ns(); + + /* + * 0 could very well be a valid time, but rather than flag "this is + * a valid timestamp" separately, just accept that we'll do an extra + * ktime_get_ns() if we just happen to get 0 as the current time. + */ + if (!plug->cur_ktime) + plug->cur_ktime = ktime_get_ns(); + return plug->cur_ktime; } static inline ktime_t blk_time_get(void) diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 99e4f5e72213..996d2ad756ff 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -942,6 +942,7 @@ struct blk_plug { /* if ios_left is > 1, we can batch tag/rq allocations */ struct request *cached_rq; + u64 cur_ktime; unsigned short nr_ios; unsigned short rq_count;