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Re: Allocating buffers in ext2fs
From: |
Roland McGrath |
Subject: |
Re: Allocating buffers in ext2fs |
Date: |
Thu, 22 Nov 2001 15:10:58 -0500 (EST) |
> Sure. Do you have a suggestions on how to gather statistics,
> i.e. other than compiling.
Not particularly. Pick some task that does the same thing every time and
does a lot of disk i/o. Compiles are such things.
> Additionally, was changing the spinlock to a mutex the right thing to do?
Ah, yes; I knew there was something I'd forgotten to respond to. That
should be fine. That kind of mmap call degenerates to vm_allocate, and so
the call can block only on the kernel and the default pager (as any
non-wired memory reference might). On a uniprocessor system, contention is
very unlikely. On an MP system, it's sufficiently rare and short that a
spin lock would not be so bad. But a mutex is certainly fine, and the
mutex implementation is optimized such that taking an uncontested mutex is
not significantly more expensive than just the spin lock.