[suse-sles-e] iscsi server TCP & sles8 high cpu usage with tcp_read_sock

From: S. K. Sammandam (sksam_at_pavitrasoft.com)
Date: Fri Feb 11 2005 - 21:11:52 CET


From: "S. K. Sammandam" <sksam@pavitrasoft.com>
Date: Fri, 11 Feb 2005 12:11:52 -0800
Message-ID: <000201c51075$ee3b2a00$0201010a@crosspt>
Subject: [suse-sles-e] iscsi server TCP & sles8 high cpu usage with tcp_read_sock

Hi,
We are working on iSCSI server and Fibre channel target for Linux based
servers and we noticed that the SLES8 kernel (even the latest 2.4.21-266) is
showing extemely high CPU usage for TCP receive only (i.e iSCSI writes from
client). With kernel profile enabled it appears that skb_copy_bits is
consuming lots of cpu (80 - 100%). The iSCSI reads from client does not
show high cpu usage and delivers 112MB/sec easily even with MTU 1500 and no
special tuning of e1000.
The same software Mayastor does NOT show high cpu usage for Redhat
Enterprise linux both on read and writes. Looks as though some patch is
missing?

SLES8 2.4.21-266
SR1330 platform, xeon 2.2 dual, Intel e1000 driver
Mayastor iscsi server
From the client we have to run bonnie++ over the iscsi disk.

Thanks in advance.
-SK

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