RE: [Xen-devel] __ia64__ ifdef in xmalloc.c: "Fix ar.unat handling forfast paths"

From: Tian, Kevin <kevin.tian_at_intel.com>
Date: 2005-11-23 13:52:55
>From: Luck, Tony
>Sent: 20051123 0:11
>This comment:
>>   /*
>>    * The "aligned" directive can only _increase_ alignment, so this is
>>    * safe and provides an easy way to avoid wasting space on a
>>    * uni-processor:
>>    */
>suggests that we only expected SMP_CACHE_BYTES to be used in "aligned"
>directives, where having a smaller value than the actual alignment
>requirement of some object would simply be ignored by the compiler.

Understand. ;-)

>
>How much is this trick saving us?  Static size of data area in
>vmlinux doesn't change very much as SMP_CACHE_BYTES is varied:
>
>   text    data     bss     dec     hex filename
>8677481 1139704 1206357 11023542         a834b6 vmlinux-8
>8677417 1141808 1206397 11025622         a83cd6 vmlinux-16
>8677417 1146000 1206477 11029894         a84d86 vmlinux-32
>8677353 1146256 1206573 11030182         a84ea6 vmlinux-64
>8677353 1163152 1207085 11047590         a892a6 vmlinux-128
>
>I'm not sure how to evaluate dynamic behavior (allocation of
>structures whose size is dependent on SMP_CACHE_BYTES at
>runtime).
>
>-Tony
>-

So maybe we can simply remove the UP specific size definition and give both cases to actual cache line size.

Thanks,
Kevin
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Received on Wed Nov 23 13:54:25 2005

This archive was generated by hypermail 2.1.8 : 2005-11-23 13:54:34 EST