Jens Axboe wrote: > On Tue, May 27 2008, Alan D. Brunelle wrote: > >> From 43c8ea2b78f31d7ccd349384a9a2084e787aafc1 Mon Sep 17 00:00:00 2001 >> From: Alan D. Brunelle <alan.brunelle@xxxxxx> >> Date: Tue, 27 May 2008 10:32:36 -0400 >> Subject: [PATCH] Changed blk trace msgs to directly use relay buffer >> >> Allows for SMP-usage without corruption, and removes an extra copy at >> the expense of copying extra bytes. Reduced message size from 1024 to 128. > > Or, alternatively, something like the below. Then we don't > unconditionally reserve and copy 128 bytes for each message, at the > cost 128 bytes per-cpu per trace. I looked into something like this, but thought the added complexity wasn't worth it. Besides the extra per-cpu stuff, you also have an extra memcopy involved - in my patch you print directly into the relay buffer. I figure that /if/ copying (128-msg_size) extra bytes is too much, one could always shrink the 128 down further. [I would think 64 bytes is probably ok.] I'd bet that the reduced complexity, and skipping the extra memcopy more than offsets having to copy a few extra bytes... Alan -- To unsubscribe from this list: send the line "unsubscribe linux-btrace" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
