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67cf13ceed
We have a large university system in the UK that is experiencing very long delays modprobing the driver for a specific I/O device. The delay is from 8-10 minutes per device and there are 31 devices in the system. This 4 to 5 hour delay in starting up those I/O devices is very much a burden on the customer. There are two causes for requiring a restart/reload of the drivers. First is periodic preventive maintenance (PM) and the second is if any of the devices experience a fatal error. Both of these trigger this excessively long delay in bringing the system back up to full capability. The problem was tracked down to a very slow IOREMAP operation and the excessively long ioresource lookup to insure that the user is not attempting to ioremap RAM. These patches provide a speed up to that function. The modprobe time appears to be affected quite a bit by previous activity on the ioresource list, which I suspect is due to cache preloading. While the overall improvement is impacted by other overhead of starting the devices, this drastically improves the modprobe time. Also our system is considerably smaller so the percentages gained will not be the same. Best case improvement with the modprobe on our 20 device smallish system was from 'real 5m51.913s' to 'real 0m18.275s'. This patch (of 2): Since the ioremap operation is verifying that the specified address range is NOT RAM, it will search the entire ioresource list if the condition is true. To make matters worse, it does this one 4k page at a time. For a 128M BAR region this is 32 passes to determine the entire region does not contain any RAM addresses. This patch provides another resource lookup function, region_is_ram, that searches for the entire region specified, verifying that it is completely contained within the resource region. If it is found, then it is checked to be RAM or not, within a single pass. The return result reflects if it was found or not (-1), and whether it is RAM (1) or not (0). This allows the caller to fallback to the previous page by page search if it was not found. [akpm@linux-foundation.org: fix spellos and typos in comment] Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Alex Thorlton <athorlton@sgi.com> Reviewed-by: Cliff Wickman <cpw@sgi.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Mark Salter <msalter@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| dt-bindings | ||
| keys | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rxrpc | ||
| scsi | ||
| soc/tegra | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| video | ||
| xen | ||
| Kbuild | ||