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ZFS writes slow with calls to arc_buf_alloc_hole()->arc_cksum_compute() (Doc ID 1988439.1)

Last updated on JULY 29, 2016

Applies to:

Solaris Operating System - Version 10 9/10 U9 to 11.2 [Release 10.0 to 11.0]
Information in this document applies to any platform.

Symptoms

File write on ZFS dataset is observed to be slow. Profiling data will show that there are frequent calls into arc_buf_cksum_compute().

The write() system call calls arc_buf_alloc_hole()->arc_cksum_compute(), resulting in write latency.

    -------------------------------------------------------------------------------
    Count indv cuml rcnt     nsec Hottest CPU+PIL        Caller
      110   0%  96% 0.00     1923 cpu[17]                fletcher_2_native

          nsec ------ Time Distribution ------ count     Stack
          2048 |@@@@@@@@@@@@@@@@@@@@           74        current_thread
          4096 |@@@@@@@@@                      36        arc_cksum_compute
                                                         arc_buf_cksum_compute
                                                         arc_buf_alloc_hole
                                                         arc_hole_ref
                                                         dbuf_read_impl
                                                         dbuf_read
                                                         dbuf_dirty_impl
                                                         dmu_assign_arcbuf
                                                         zfs_write
                                                         fop_write
                                                         write
                                                         syscall_trap32
   

 

 

Changes

Customer has recently applied zfs patch 150125-03 (sparc) or 149637-03 (x86) or later, but without 150400-21(sparc) or 150401-21(x86).

Cause

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In this Document
Symptoms
Changes
Cause
Solution
References


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