draft/wip: lsdevinfo performance #97
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We can avoid spawning subprocesses by using the 'read' builtin. Signed-off-by: Nathan Lynch <[email protected]>
Use '!' for the substitution delimiter when manipulating path strings that contain '/'. This will make such code more amenable to mechanical transformations to come. Signed-off-by: Nathan Lynch <[email protected]>
There is no reason to repeatedly spell out "/proc/device-tree". Signed-off-by: Nathan Lynch <[email protected]>
The same work is performed to set the "slot" and "connection" variables in the vscsi and vfc loops; eliminate the duplication. Signed-off-by: Nathan Lynch <[email protected]>
The "connection" variables are just the OF unit addresses (following the "@" in the node name). Use shell parameter expansion to efficiently extract these from variables containing the paths. Signed-off-by: Nathan Lynch <[email protected]>
Using redirection and the read builtin suffices.
[root@ltc-zz14-lp1 ~]# strace -q -f -c -e wait4,clone,execve,pipe2 /usr/sbin/lsdevinfo -F name
device:
name="env2"
device:
name="host0"
device:
name="sda"
/bin/ls: cannot access '/sys/devices/vio/30000004/host*': No such file or directory
device:
name="host1"
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
96.98 0.387740 1664 233 110 wait4
2.17 0.008676 70 123 clone
0.70 0.002815 37 75 execve
0.14 0.000567 7 81 pipe2
------ ----------- ----------- --------- --------- ----------------
100.00 0.399798 780 512 110 total
Signed-off-by: Nathan Lynch <[email protected]>
The pipeline is inefficient (multiple grep invocations) and
fragile (excluding names we're not interested in instead of just
specifying a name that matches what we want). Replace it with a shell
glob into an array.
[root@ltc-zz14-lp1 ~]# strace -q -f -c -e wait4,clone,execve,pipe2 lsdevinfo -F name
device:
name="env2"
device:
name="host0"
device:
name="sda"
/bin/ls: cannot access '/sys/devices/vio/30000004/host*': No such file or directory
device:
name="host1"
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
97.15 0.308000 1387 222 106 wait4
2.07 0.006572 56 116 clone
0.66 0.002080 29 70 execve
0.12 0.000384 5 75 pipe2
------ ----------- ----------- --------- --------- ----------------
100.00 0.317036 656 483 106 total
Signed-off-by: Nathan Lynch <[email protected]>
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Attempts at reducing the number of external processes spawned.
Work in progress for now, lightly tested.