[jira] [Updated] (TS-4316) Slot accelerator doesn't effect under certain condition

["Alan M. Carroll (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TS-4316?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alan M. Carroll updated TS-4316:
--------------------------------
    Fix Version/s:     (was: 7.0.0)
                   sometime

> Slot accelerator doesn't effect under certain condition
> -------------------------------------------------------
>
>                 Key: TS-4316
>                 URL: https://issues.apache.org/jira/browse/TS-4316
>             Project: Traffic Server
>          Issue Type: Bug
>          Components: MIME
>            Reporter: Masakazu Kitajo
>            Assignee: Alan M. Carroll
>             Fix For: sometime
>
>
> Slot accelerators seem to not effect if the stored slot number is 14 or 15.
> This is because {{mime_hdr_set_accelerators_and_presence_bits()}} regards slot number 14+ as "unknown" and stores MIME_FIELD_SLOTNUM_UNKNOWN(14) to an accelerator, and it causes slower search. Although there is no critical effect, it would decreases performance slightly.
> The numbers, 14 and 15, comes from constants below in MIME.h:
> {code}
> #define MIME_FIELD_SLOTNUM_BITS 4
> #define MIME_FIELD_SLOTNUM_MASK ((1 << MIME_FIELD_SLOTNUM_BITS) - 1)
> #define MIME_FIELD_SLOTNUM_MAX (MIME_FIELD_SLOTNUM_MASK - 1)
> #define MIME_FIELD_SLOTNUM_UNKNOWN MIME_FIELD_SLOTNUM_MAX
> {code}
> MIME_FIELD_SLOTNUM_MASK is 15.
> MIME_FIELD_SLOTNUM_MAX is 14.
> MIME_FIELD_SLOTNUM_UNKNOWN is 14 too.
> Though it still needs more careful confirmation, it seems we can simply change {{MIME_FIELD_SLOTNUM_UNKNOWN}} to the value of {{MIME_FIELD_SLOTNUM_MASK}} (15). But we still cannot use 15.
> To use 15 as a valid slot number in slot accelerators, we need to change {{MIME_FIELD_SLOTNUM_UNKNOWN}} to 16 or -1, however it would need to change some codes also (not only the number).
> This bug has been found while I was tackling TS-4313.
> https://github.com/apache/trafficserver/pull/542#discussion-diff-58226891



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