I posted this patch today on linux-arm-kernel, but I repeat it here because there does not seem to be too much interest on that list for the ARM FCSE.
I also tried to combine this patch with ipipe for kernel 2.6.20 running on the Intel IXDP465, but after booting I soon get a BUG. Anyhow, perhaps the ARM people might take a look at combining ipipe with FCSE... -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Richard Cochran Sent: Friday, March 07, 2008 4:52 PM To: [EMAIL PROTECTED] Subject: [PATCH] repost: ARM FCSE It looks like my mailer just wrapped the line endings, and I don't know how to make it stop! (How does one escape from Outlook + Exchange?) Here is the patch once again, as an attachment. Richard --- This patch implements the ARM FCSE for Linux in a minimally intrusive way. The patch is against kernel 2.6.24, but it will also work with other recent kernels. I have tested the patch on the following machine/kernel combinations. Linksys NSLU2 2.6.21 Omicron DEVXIP 2.6.23 (this board is similar to the IXDP425) Intel IXDP465 2.6.24 Using the patch, I measured an improvement in the task switching time of about 100 us on all three platforms. The test program does something like this: 1. blocking read on network socket 2. process packet 3. send reply packet I externally measured the time from the input packet to appear on the line until the reply packet appear. I attribute the improvement in response time to the faster scheduling, due to the FCSE. KNOWN ISSUES: 1. The avoidance of flushing the D/I caches is only implemented for Xscale, in arch/arm/mm/proc-xscale.S. If you want to try other types, you should make similar changes for that type, otherwise enabling FCSE only limits your machine with no performance benefit. 2. The patch limits the total number of PIDs to 96, including each kernel and user thread. This is a bit wasteful, and it could be improved. 3. On the NSLU2, the 'ldconfig' program hangs after calling MMAP2(2) many times, but I do not know why. Looking forward to your comments, Richard
fcse.diff
Description: fcse.diff
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