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authorMike Marciniszyn <mike.marciniszyn@qlogic.com>2011-07-21 13:21:16 +0000
committerRoland Dreier <roland@purestorage.com>2011-07-22 11:56:05 -0700
commite67306a38063d75f61d405527ff8bf1c8e92eb84 (patch)
treed40991481f25dea940bd549524a10679cbbe5699 /drivers/net/wireless/wl12xx/tx.h
parente800bd032c2623b10ef38a4d7d646e3e3c7bb3ad (diff)
IB/qib: Defer HCA error events to tasklet
With ib_qib options: options ib_qib krcvqs=1 pcie_caps=0x51 rcvhdrcnt=4096 singleport=1 ibmtu=4 a run of ib_write_bw -a yields the following: ------------------------------------------------------------------ #bytes #iterations BW peak[MB/sec] BW average[MB/sec] 1048576 5000 2910.64 229.80 ------------------------------------------------------------------ The top cpu use in a profile is: CPU: Intel Architectural Perfmon, speed 2400.15 MHz (estimated) Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 1002300 Counted LLC_MISSES events (Last level cache demand requests from this core that missed the LLC) with a unit mask of 0x41 (No unit mask) count 10000 samples % samples % app name symbol name 15237 29.2642 964 17.1195 ib_qib.ko qib_7322intr 12320 23.6618 1040 18.4692 ib_qib.ko handle_7322_errors 4106 7.8860 0 0 vmlinux vsnprintf Analysis of the stats, profile, the code, and the annotated profile indicate: - All of the overflow interrupts (one per packet overflow) are serviced on CPU0 with no mitigation on the frequency. - All of the receive interrupts are being serviced by CPU0. (That is the way truescale.cmds statically allocates the kctx IRQs to CPU) - The code is spending all of its time servicing QIB_I_C_ERROR RcvEgrFullErr interrupts on CPU0, starving the packet receive processing. - The decode_err routine is very inefficient, using a printf variant to format a "%s" and continues to loop when the errs mask has been cleared. - Both qib_7322intr and handle_7322_errors read pci registers, which is very inefficient. The fix does the following: - Adds a tasklet to service QIB_I_C_ERROR - Replaces the very inefficient scnprintf() with a memcpy(). A field is added to qib_hwerror_msgs to save the sizeof("string") at compile time so that a strlen is not needed during err_decode(). - The most frequent errors (Overflows) are serviced first to exit the loop as early as possible. - The loop now exits as soon as the errs mask is clear rather than fruitlessly looping through the msp array. With this fix the performance changes to: ------------------------------------------------------------------ #bytes #iterations BW peak[MB/sec] BW average[MB/sec] 1048576 5000 2990.64 2941.35 ------------------------------------------------------------------ During testing of the error handling overflow patch, it was determined that some CPU's were slower when servicing both overflow and receive interrupts on CPU0 with different MSI interrupt vectors. This patch adds an option (krcvq01_no_msi) to not use a dedicated MSI interrupt for kctx's < 2 and to service them on the default interrupt. For some CPUs, the cost of the interrupt enter/exit is more costly than then the additional PCI read in the default handler. Signed-off-by: Mike Marciniszyn <mike.marciniszyn@qlogic.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
Diffstat (limited to 'drivers/net/wireless/wl12xx/tx.h')
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