Messages in this thread | | | Date | Wed, 19 May 1999 12:20:10 +0200 (CEST) | From | Andrea Arcangeli <> | Subject | Re: andrea buffer code (2.2.9-C.gz) |
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On Wed, 19 May 1999, Manfred Spraul wrote:
>I noticed that you added a new spinlock to every memmap_t, >i.e. 4 bytes for every 4096 bytes system memory.
Yes.
>Is that really required? Have you made any profiling?
If you want to SMP scale well it's needed (I don't think on a two-way SMP is a big issue having a per-memmap spinlock instead of a global spinlock but on more powerful machines it can help I think).
The point is that there we don't need a global spinlock but there we can scale far more finegriend on per-page basis. If our approch is to scale well as possible in SMP without bother to waste some more kbyte of memory the spinlock it's required. You know: to scale better you need to waste more memory :-).
An UP compile done with a not-buggy compiler won't waste a bit of memory though.
>The spinlock is only acquired for a few lines, >perhaps one global spinlock would save memory.
Yes but I am not worried, and being more finegrined in SMP is more fun :-).
Andrea Arcangeli
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