From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Wed, 03 Sep 2003 02:00:31 +0000 Subject: Re: SHMLBA on linux-ia64 Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Tue, 2 Sep 2003 17:33:15 -0700, Umut Aymakoglu said: Umut> Hi - The file /usr/include/sys/shm.h defines SHMLBA as Umut> __getpagesize() which is 16K. Must be an old libc. For example, with glibc v2.3.2, I see: $ fgrep 'e SHMLBA' /usr/include/bits/shm.h #define SHMLBA (1024 * 1024) Umut> whereas in /usr/include/asm/shmparam.h thereis another define Umut> of SHMLBA as (1024*1024) and a comment saying on IA-64 Umut> architecture due to some performance problems it is better to Umut> use this alignment. Not "performance problem" but "_potential_ performance degradation". On existing ia64 processors, you won't see a performance degradation, but it is nevertheless recommend to align shared mappings to a 1MB boundary because the architecture reserves the right that some future CPU might run slower when there is a virtual alias that is not congruent modulo 1MB. --david