{"id":2220961,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2220961/?format=json","web_url":"http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20260408131216.2662245-4-aleksandr.loktionov@intel.com/","project":{"id":46,"url":"http://patchwork.ozlabs.org/api/1.1/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":""},"msgid":"<20260408131216.2662245-4-aleksandr.loktionov@intel.com>","date":"2026-04-08T13:12:11","name":"[iwl-next,v2,3/8] ixgbe: limit ITR decrease in latency mode to prevent ACK overdrive","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"9e1fb4304ec2c99e5d9068d5c70361e3b1a12713","submitter":{"id":75597,"url":"http://patchwork.ozlabs.org/api/1.1/people/75597/?format=json","name":"Loktionov, Aleksandr","email":"aleksandr.loktionov@intel.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20260408131216.2662245-4-aleksandr.loktionov@intel.com/mbox/","series":[{"id":499140,"url":"http://patchwork.ozlabs.org/api/1.1/series/499140/?format=json","web_url":"http://patchwork.ozlabs.org/project/intel-wired-lan/list/?series=499140","date":"2026-04-08T13:12:08","name":"ixgbe: nits and improvements","version":2,"mbox":"http://patchwork.ozlabs.org/series/499140/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2220961/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2220961/checks/","tags":{},"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=rKcf8xh5;\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=\"102087269\"","E=Sophos;i=\"6.23,167,1770624000\"; d=\"scan'208\";a=\"102087269\"","E=Sophos;i=\"6.23,167,1770624000\"; d=\"scan'208\";a=\"228715079\""],"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":"Wed, 8 Apr 2026 15:12:11 +0200","Message-ID":"<20260408131216.2662245-4-aleksandr.loktionov@intel.com>","X-Mailer":"git-send-email 2.52.0","In-Reply-To":"<20260408131216.2662245-1-aleksandr.loktionov@intel.com>","References":"<20260408131216.2662245-1-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=1775653943; x=1807189943;\n h=from:to:cc:subject:date:message-id:in-reply-to:\n references:mime-version:content-transfer-encoding;\n bh=0eZTH5jLMaLPvyw05d6AwXy0c332K5yiwSJKtS18gg0=;\n b=SSaOFx5He0LUVnu3K3U/877T2LuxZrFgjXt2kNP6XEbvIrK8c+LQRTRE\n OZxwLE/2Wnaqe9T1kdx0o854GY4slSPdV5nGcFhVIVvN2pbCgwEJWZoCb\n OGoiwpW7bwibOsxWLlbJ6ehrspVknZ8paJJDxtbt+Edg8JISfQirPQAUd\n eGCB0E6wo175Y2wTsMzoWljBm+AK7T3ibQa+T3ucuWomAd4hZ0MWYqeRd\n 7t0uJPUM0Newa1s2GkFsJ58mo8orP691yIfeSjYLGENFMDqb4k9mMYZ5u\n 01IU435iCODZYYCOi6NZwMYdbFybxmW55X8PDmnqWiUEXeNXsQ/cLTsQs\n A==;","X-Mailman-Original-Authentication-Results":["smtp4.osuosl.org;\n dmarc=pass (p=none dis=none)\n header.from=intel.com","smtp4.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=SSaOFx5H"],"Subject":"[Intel-wired-lan] [PATCH iwl-next v2 3/8] ixgbe: limit ITR decrease\n in 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---\nv1 -> v2:\n - Split from monolithic ITR cleanup; this patch only adds the 2 us\n per-step decrease limit for latency-mode workloads.\n\n drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 9 +++++++++\n 1 file changed, 9 insertions(+)","diff":"diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\nindex b3f4a72..d7c5e83 100644\n--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\n+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\n@@ -2888,6 +2888,16 @@ 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 = 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","v2","3/8"]}