[ccache] Ccache prefetch

Ian Albany albo123 at yandex.com
Sun May 11 00:15:50 MDT 2014


Hi

I guest you missed my point. I believe that the discrepancy between "memory" caches and "disk" caches on a typical harvard architecture these days is such that I derive great benefits by reading the later into the former via another thread on the same build machine.

I do derive a measure of improvement, but not as great as I derive from subsequent builds after a reboot than I do after the former. So my point is, I guess, is there any way to ccache to know the locality of hits for a given object and therefore preload those objects which would entail a separate thread of execution.

I know this adds some complexity but in effect, I would say that when I build the kernel, I am usually hitting the cache in a normally pretty predetermined order.

Yes but running everything in tmpfs on a 32GB system everything does fly.

Alby  

11.05.2014, 15:51, "Eitan Adler" <lists at eitanadler.com>:
> On 10 May 2014 22:11, Ian Albany <albo123 at yandex.com> wrote:
>
>>  Hi
>>
>>  I have what prima facie appears to be a bit of a silly question about ccache. But first, let me just say that I have been uging ccache for over a decade and I am quite happy overall.
>>
>>  However, during many compiltaions I notice that the build time on linux at least varies and I have pinned it down to the fact that most of the blocking withing ccache with my current setup occurs with disk IO.
>
> I can not speak to Linux but have you tried putting the cache on a
> tmpfs or mdfs partition?  In addition do you find that existing disk
> caching does not help you?
>
> --
> Eitan Adler


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