{"id":2234733,"url":"http://patchwork.ozlabs.org/api/1.2/patches/2234733/?format=json","web_url":"http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20260508031226.3601800-8-aleksandr.loktionov@intel.com/","project":{"id":46,"url":"http://patchwork.ozlabs.org/api/1.2/projects/46/?format=json","name":"Intel Wired Ethernet development","link_name":"intel-wired-lan","list_id":"intel-wired-lan.osuosl.org","list_email":"intel-wired-lan@osuosl.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260508031226.3601800-8-aleksandr.loktionov@intel.com>","list_archive_url":null,"date":"2026-05-08T03:12:25","name":"[iwl-next,7/8] ixgbe: limit ITR decrease in latency mode to prevent ACK overdrive","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"b30478319aa20aebf9cd749e653fccebb7c0c12c","submitter":{"id":75597,"url":"http://patchwork.ozlabs.org/api/1.2/people/75597/?format=json","name":"Loktionov, Aleksandr","email":"aleksandr.loktionov@intel.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20260508031226.3601800-8-aleksandr.loktionov@intel.com/mbox/","series":[{"id":503311,"url":"http://patchwork.ozlabs.org/api/1.2/series/503311/?format=json","web_url":"http://patchwork.ozlabs.org/project/intel-wired-lan/list/?series=503311","date":"2026-05-08T03:12:18","name":"ixgbe: small cleanups and improvements","version":1,"mbox":"http://patchwork.ozlabs.org/series/503311/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2234733/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2234733/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","intel-wired-lan@lists.osuosl.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","intel-wired-lan@lists.osuosl.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=osuosl.org header.i=@osuosl.org header.a=rsa-sha256\n header.s=default header.b=orpk7hXF;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=osuosl.org\n (client-ip=2605:bc80:3010::137; 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a=\"79027520\"","E=Sophos;i=\"6.23,222,1770624000\"; d=\"scan'208\";a=\"79027520\"","E=Sophos;i=\"6.23,222,1770624000\"; d=\"scan'208\";a=\"241623218\""],"X-ExtLoop1":"1","From":"Aleksandr Loktionov ","To":"intel-wired-lan@lists.osuosl.org, anthony.l.nguyen@intel.com,\n aleksandr.loktionov@intel.com","Cc":"netdev@vger.kernel.org","Date":"Fri, 8 May 2026 05:12:25 +0200","Message-ID":"<20260508031226.3601800-8-aleksandr.loktionov@intel.com>","X-Mailer":"git-send-email 2.52.0","In-Reply-To":"<20260508031226.3601800-1-aleksandr.loktionov@intel.com>","References":"<20260508031226.3601800-1-aleksandr.loktionov@intel.com>","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-Mailman-Original-DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple;\n d=intel.com; i=@intel.com; q=dns/txt; s=Intel;\n t=1778209960; x=1809745960;\n h=from:to:cc:subject:date:message-id:in-reply-to:\n references:mime-version:content-transfer-encoding;\n bh=eC/N+PKSldiwuiYBHXeNZDIr7XUuCPxaNishs9wb0RI=;\n b=mIsLoWxVSz9QcU3mG6A4QI926Z/H7je4EQd2m4D1Eb+O6iBQmpSLeA0R\n lIcjfyjMpuk5dLrBR9C4jvUszku8ewmQIj0cS0vHbGPAu0TB2YSR2bBH0\n FZy7SOImC/sRJcccGDEWA6HPrHI8V7vFj/+3a3mzu2ed6QVKlS6Cv3WUi\n 7G9zJfCDpivB2E6BnBcL7TAOuLPl0mSGoEmHPeqbo7z9ad6D9PYDQKCLN\n g022rW/5YpHgHPS7/xZbUrfIzCDoxGsw8s+CKikeljmNY6bADUDR+wSTV\n 7m0gM+SjV29LyhEHWDi/IRQikwyA4n9gAFkg/unmKqDH7Dnv4ltT9FRtJ\n g==;","X-Mailman-Original-Authentication-Results":["smtp2.osuosl.org;\n dmarc=pass (p=none dis=none)\n header.from=intel.com","smtp2.osuosl.org;\n dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com\n header.a=rsa-sha256 header.s=Intel header.b=mIsLoWxV"],"Subject":"[Intel-wired-lan] [PATCH iwl-next 7/8] ixgbe: limit ITR decrease in\n latency mode to prevent ACK overdrive","X-BeenThere":"intel-wired-lan@osuosl.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Intel Wired Ethernet Linux Kernel Driver Development\n ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"intel-wired-lan-bounces@osuosl.org","Sender":"\"Intel-wired-lan\" "},"content":"From: Alexander Duyck \n\nWhen operating in latency mode and the computed ITR is lower than the\ncurrent setting, the algorithm can reduce the interrupt rate too\naggressively in a single step. For a TCP workload this means the ACK\nstream (a latency-sensitive, low-packet-rate workload) can drive the\nmoderation down to very high interrupt rates, starving CPU time from\nthe sender side.\n\nAfter the speed-based ITR calculation is complete, check whether the\nresult is in latency mode and would decrease below the current setting.\nIf so, limit the decrease to at most IXGBE_ITR_ADAPTIVE_MIN_INC (2 us)\nper update. This ensures the number of interrupts grows by no more\nthan 2x per adjustment step for latency-class workloads, dialling in\nsmoothly rather than overshooting.\n\nSigned-off-by: Alexander Duyck \nSigned-off-by: Aleksandr Loktionov \n---\n drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 11 +++++++++++\n 1 file changed, 11 insertions(+)","diff":"diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\nindex aea76b3..ba7b013 100644\n--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\n+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\n@@ -2888,6 +2888,17 @@ static void ixgbe_update_itr(struct ixgbe_q_vector *q_vector,\n \t\tbreak;\n \t}\n \n+\t/* In the case of a latency specific workload only allow us to\n+\t * reduce the ITR by at most 2us. By doing this we should dial\n+\t * in so that our number of interrupts is no more than 2x the number\n+\t * of packets for the least busy workload. So for example in the case\n+\t * of a TCP workload the ACK packets being received would set the\n+\t * interrupt rate as they are a latency specific workload.\n+\t */\n+\tif ((itr & IXGBE_ITR_ADAPTIVE_LATENCY) && itr < ring_container->itr)\n+\t\titr = max_t(unsigned int, itr,\n+\t\t\t ring_container->itr - IXGBE_ITR_ADAPTIVE_MIN_INC);\n+\n clear_counts:\n \t/* write back value */\n \tring_container->itr = itr;\n","prefixes":["iwl-next","7/8"]}