In several functions, vtbuf_putchar() in particular, the lock on vtbuf
is acquired twice:
1. once by the said functions;
2. once in vtbuf_dirty().
Now, vtbuf_dirty_locked() and vtbuf_dirty_cell_locked() allow to
acquire that lock only once.
This improves the input speed of vt(4). To measure the gain, a
50,000-lines file was displayed on the console using cat(1). The time
taken by cat(1) is reported below:
o On amd64, with vt_vga:
- before: 1.0"
- after: 0.5"
o On sparc64, with creator_vt:
- before: 13.6"
- after: 10.5"
MFC after: 1 week
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