From patchwork Mon Jan 23 14:37:19 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Begunkov X-Patchwork-Id: 13112305 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE89DC05027 for ; Mon, 23 Jan 2023 14:42:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231492AbjAWOmR (ORCPT ); Mon, 23 Jan 2023 09:42:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49510 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231274AbjAWOmP (ORCPT ); Mon, 23 Jan 2023 09:42:15 -0500 Received: from mail-wr1-x431.google.com (mail-wr1-x431.google.com [IPv6:2a00:1450:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A4DD121A0F for ; Mon, 23 Jan 2023 06:42:14 -0800 (PST) Received: by mail-wr1-x431.google.com with SMTP id d14so7338802wrr.9 for ; Mon, 23 Jan 2023 06:42:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; 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=SCWbGwBl576a0ArFhLpktKBP44fCtoi8yPjJSutd26c=; b=Ru+NvOrZat8Q4naKOvtZZE5eIJ0xQ0ktc27fRXyv1tWCfYZEeL6BwWHbFc5XMxDK8L Fvw/NETP+ei3HtMs11TOtLptJniwvp6fv/oslYqvT8wGjWXB+Vik+s/sHyMU4LgtqDOL RGy6FZU/M9yRMeOBq2VGEgrZ2KCsn06xEusVTRSo8Ej9+dWLmAWr6w9K/a8/JASo62HT 3ctXv8rQiFFCgUM+XeEiOLqN4n10h6S3eYFLt3yui6StqDcO/9GIcXE6PymWrImJe8ut FOFdw7PN3BSEizvYg3bDzPqJ8keFFN7Ju3dykLB8YmIGR9QEIq1vzINXJoZQSQkCS1AR Tcew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; 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=SCWbGwBl576a0ArFhLpktKBP44fCtoi8yPjJSutd26c=; b=N8PPRsK7zEBKuxXEEprCpJbg7Zaot9/Sqr/dHHwk3LzTysok0MM7W3lsf1NQolMFr1 GQvjCat+NBQxXTS6C7f5YxlctqXPs3k+OsIhmM+Xp/5EcFhAeNIoDi4R4DnA19kgEa1O 5fRIVX83vM9W96h0kkCk7YZoY7qWbNxez1wBwOxDNNUu1HqQyw4mdB6FTVcfjs/WMKQO p1WFY9La42ezDpyA72833NWxtyGla661ZKGVMiN/TWmiPl8oysFVjTOuG1t/pfSOSHzI jcygCXgR00eRjF0VVsaGdkfJTdbBa+34XNoAbxr6x+5yUMNUxDzxa+71j9+9n5u6xmyK 1e2w== X-Gm-Message-State: AFqh2kpzIwdVRy78d3pRcaxsivYtSc/vGIAdg/eDufYdFHfoW9QwF69l 6fmza6GYNvazjO0FWGudPZMfYUgU8bw= X-Google-Smtp-Source: AMrXdXuvIa4UQlMVSHG3GUuF92gxi34AWjhovyqIk3PSEPm1SxEdb02kvaSX6HTAaq1kJrnL16f3/g== X-Received: by 2002:adf:f7c5:0:b0:2be:5a87:4e5 with SMTP id a5-20020adff7c5000000b002be5a8704e5mr10641777wrq.12.1674484934079; Mon, 23 Jan 2023 06:42:14 -0800 (PST) Received: from 127.0.0.1localhost (188.30.84.186.threembb.co.uk. [188.30.84.186]) by smtp.gmail.com with ESMTPSA id d24-20020adfa358000000b00236883f2f5csm3250534wrb.94.2023.01.23.06.42.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Jan 2023 06:42:13 -0800 (PST) From: Pavel Begunkov To: io-uring@vger.kernel.org Cc: Jens Axboe , asml.silence@gmail.com Subject: [PATCH for-next 7/7] io_uring: return normal tw run linking optimisation Date: Mon, 23 Jan 2023 14:37:19 +0000 Message-Id: X-Mailer: git-send-email 2.38.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org io_submit_flush_completions() may produce new task_work items, so it's a good idea to recheck the task_work list after flushing completions. The optimisation is not new and was accidentially removed by f88262e60bb9 ("io_uring: lockless task list") Signed-off-by: Pavel Begunkov --- io_uring/io_uring.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 586e70f686ce..8c4d92e64c20 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1238,6 +1238,15 @@ void tctx_task_work(struct callback_head *cb) loops++; node = io_llist_xchg(&tctx->task_list, &fake); count += handle_tw_list(node, &ctx, &uring_locked, &fake); + + /* skip expensive cmpxchg if there are items in the list */ + if (READ_ONCE(tctx->task_list.first) != &fake) + continue; + if (uring_locked && !wq_list_empty(&ctx->submit_state.compl_reqs)) { + io_submit_flush_completions(ctx); + if (READ_ONCE(tctx->task_list.first) != &fake) + continue; + } node = io_llist_cmpxchg(&tctx->task_list, &fake, NULL); } while (node != &fake);