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 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 60D97C9830D for ; Fri, 25 Sep 2026 15:10:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xA7YM-0000H5-JA; Fri, 25 Sep 2026 11:09:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xA7YK-0000GO-JR for qemu-devel@nongnu.org; Fri, 25 Sep 2026 11:09:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xA7YI-0001Mg-J3 for qemu-devel@nongnu.org; Fri, 25 Sep 2026 11:09:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1790348969; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3kZ3KiyS6g3PynDQfawPhQdd55pp7R8FUVSyiOB2Rck=; b=KOT/9OlLeBSim1kHidC7JW0Xfktqv8yFYgoVjJ1ma8iDsVY7Mf8Sze2ZsXL15H4KHd3m+v ckiNzE8aQnGsyeiT3ifAIAGtAmu9oK89X9hJbA5WS+nF0hU1WK6x+ZPLAK6EcX21710qvM SqRhqK+uW4n+4bIBl9DEWYt6YwNYw7g= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-378-9vqtT9BqM5ee3c21knB0-Q-1; Fri, 25 Sep 2026 11:09:27 -0400 X-MC-Unique: 9vqtT9BqM5ee3c21knB0-Q-1 X-Mimecast-MFC-AGG-ID: 9vqtT9BqM5ee3c21knB0-Q_1790348966 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AA575194A21C; Fri, 25 Sep 2026 15:09:09 +0000 (UTC) Received: from redhat.com (unknown [10.44.32.175]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CE12518004D4; Fri, 25 Sep 2026 15:09:07 +0000 (UTC) Date: Fri, 25 Sep 2026 17:09:05 +0200 From: Kevin Wolf To: Jorge Merlino Cc: qemu-devel@nongnu.org, Hanna Reitz , qemu-block@nongnu.org Subject: Re: [PATCH] block: add debug when block operations finish Message-ID: References: <20260909-debug-block-ops-b4-v1-1-2405f34ec068@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260909-debug-block-ops-b4-v1-1-2405f34ec068@canonical.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 09.09.2026 um 21:56 hat Jorge Merlino geschrieben: > Add new debug tracepoints when block read and write operations finish to > be able to measure latency. > > Signed-off-by: Jorge Merlino The subject line should mention trace points. Maybe just "block: Add tracepoiont at end of read/write"? > This patch adds debug tracepoints when block read and write operations > finish. The log includes the parameters used when the operation was > initiated so that the start and finish messages can be easily > correlated. Also the return value of the operation is logged. > > This can be used to analyze latency issues with block operations. Yes, this seems useful. I wonder if we shouldn't make sure that the start and end traces always come in pairs. Specifically... > block/block-backend.c | 2 ++ > block/trace-events | 2 ++ > 2 files changed, 4 insertions(+) > > diff --git a/block/block-backend.c b/block/block-backend.c > index 37ba7e9fc4..75d3cd1949 100644 > --- a/block/block-backend.c > +++ b/block/block-backend.c > @@ -1364,6 +1364,7 @@ blk_co_do_preadv_part(BlockBackend *blk, int64_t offset, int64_t bytes, Adding more context here: trace_blk_co_preadv(blk, bs, offset, bytes, flags); ret = blk_check_byte_request(blk, offset, bytes); if (ret < 0) { return ret; } Should this error return also call trace_blk_co_preadv_done()? bdrv_inc_in_flight(bs); /* throttling disk I/O */ if (qatomic_load_acquire(&tgm->throttle_state)) { throttle_group_co_io_limits_intercept(tgm, bytes, THROTTLE_READ); } > > ret = bdrv_co_preadv_part(blk->root, offset, bytes, qiov, qiov_offset, > flags); > + trace_blk_co_preadv_done(blk, bs, offset, bytes, ret); > bdrv_dec_in_flight(bs); > return ret; > } > @@ -1442,6 +1443,7 @@ blk_co_do_pwritev_part(BlockBackend *blk, int64_t offset, int64_t bytes, > > ret = bdrv_co_pwritev_part(blk->root, offset, bytes, qiov, qiov_offset, > flags); > + trace_blk_co_pwritev_done(blk, bs, offset, bytes, ret); > bdrv_dec_in_flight(bs); > return ret; > } Same question for writes. Kevin