Read-only source files (was: Re: [squeak-dev] Why is source code always in files only?)

Eliot Miranda eliot.miranda at gmail.com
Tue Jan 20 01:18:05 UTC 2015


On Mon, Jan 19, 2015 at 5:09 PM, Levente Uzonyi <leves at elte.hu> wrote:

> On Mon, 19 Jan 2015, Eliot Miranda wrote:
>
>
>>
>> On Mon, Jan 19, 2015 at 1:31 PM, Nicolas Cellier <
>> nicolas.cellier.aka.nice at gmail.com> wrote:
>>       Hi Tobias,
>>       are you aware of CurrentReadOnlySourceFiles cacheDuring: [...]
>> This is to workaround the readOnlyCopy used for thread safety which is
>> the main killer of performance...
>>
>>
>> IMO this is a bug.  We should simply have a single read-only copy of each
>> sources file and modify the debugger to either save and restore the state
>> of a read-only copy around accessing source, or use its own
>> read-only copy (except that the latter approach breaks when one debugs
>> the debugger).  The difference in performance between using
>> CurrentReadOnlySourceFiles cacheDuring: [...] and not in anything that
>> accesses source is huge.  And CurrentReadOnlySourceFiles cacheDuring:
>> [...] is a /lot/ of verbiage to type in doits, and a sign that something is
>> wrong.
>>
>
> How would using a single copy solve the concurrency issues?
>

It wouldn't, but what issues are you seeing in concurrent source access?
VW doesn't even have read-only copies and AFAICR we never had complaints
about this.  Is there really a thread-safety issue here?


>
> I think the real solution would be to use per process copies, which were
> initialized lazily, and were closed automatically after some time of
> inactivity.


If concurrent access was really an issue then OK.  But first I'd like some
evidence that there's a real problem here.
-- 
best,
Eliot
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