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Date: Thu, 7 Sep 2006 05:11:20 -0600 From: Matthew Wilcox <matthew@....cx> To: Tejun Heo <htejun@...il.com> Cc: linux-pci@...ey.karlin.mff.cuni.cz, Greg KH <greg@...ah.com>, lkml <linux-kernel@...r.kernel.org> Subject: Re: question regarding cacheline size On Thu, Sep 07, 2006 at 10:31:02AM +0200, Tejun Heo wrote: > As the BIOS doesn't run after hotplugging cardbus card, the cache line > isn't configured and the controller ends up having 0 cache line size and > always using Read command. When that happens, write performance drops > hard - the throughput is < 2Mbytes/s. > > http://thread.gmane.org/gmane.linux.ide/12908/focus=12908 > > So, sata_sil24 driver has to program CLS if it's not already set, but > I'm not sure which number to punch in. FWIW, sil3124 doesn't seem to > put restrictions on the values which can be used for CLS. There are > several candidates... > > * L1_CACHE_BYTES / 4 : this is used by init routine in yenta_socket.c. > It seems to be a sane default but I'm not sure whether L1 cache line > size always coincides with the size as seen from PCI bus. > > * pci_cache_line_size in drivers/pci/pci.c : this is used for > pci_generic_prep_mwi() and can be overridden by arch specific code. > this seems more appropriate but is not exported. > > For all involved commands - memory read line, memory read multiple and > memory write and invalidate - a value larger than actual cacheline size > doesn't hurt but a smaller value may. Just call pci_set_mwi(), that'll make sure the cache line size is set correctly. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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