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Re: [Qemu-devel] [PATCH] Huge TLB performance improvement
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH] Huge TLB performance improvement |
Date: |
Sun, 12 Nov 2006 14:44:46 +0000 |
User-agent: |
KMail/1.9.5 |
> > Other targets have a hardware managed TLB. On a hardware managed TLB the
> > OS treats it as if it were infinite size, and invalidation only occurs
> > when a OS changes the mappings. On a software managed TLB "flushes" are
> > more likely to occur during normal operation as TLB slots are reused.
>
> The excessive flushing for mips happens because Qemu doesn't properly
> model the hardware's ASID handling.
Are you sure? IIUC changing the ASID causes a full qemu TLB flush. The code
we're tweaking here is for single page flush.
Actually that gives me an idea. When a TLB entry with a different ASID gets
evicted we currently flush that page. This should be a no-op because we
already did a full flush when the ASID changed.
The other explanation is that the gest OS is manually doing a full TLB flush
by manually evicting all the TLB entries. I'd hope that a sane guest OS would
only do that as a last resort though.
Paul
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Daniel Jacobowitz, 2006/11/05
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Daniel Jacobowitz, 2006/11/11
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Laurent Desnogues, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Thiemo Seufer, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Paul Brook, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Thiemo Seufer, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement,
Paul Brook <=
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Daniel Jacobowitz, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Daniel Jacobowitz, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Thiemo Seufer, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Daniel Jacobowitz, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Daniel Jacobowitz, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Dirk Behme, 2006/11/12
- Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Daniel Jacobowitz, 2006/11/12
Re: [Qemu-devel] [PATCH] Huge TLB performance improvement, Paul Brook, 2006/11/12